I can reproduce this 100% by making Okular produce two sound notifications (not very quickly one after the other) 

I'll be reporting this to gstreamer too

Thread 21 "queue0:src" received signal SIGPIPE, Broken pipe.

Thread 24 (Thread 0x7fff9ffff700 (LWP 28566)):
#0  0x00007ffff3c750f9 in syscall () at /usr/lib/libc.so.6
#1  0x00007fffee69e52d in g_cond_wait_until () at /usr/lib/libglib-2.0.so.0
#2  0x00007fffee629903 in  () at /usr/lib/libglib-2.0.so.0
#3  0x00007fffee680436 in  () at /usr/lib/libglib-2.0.so.0
#4  0x00007fffee67fa2a in  () at /usr/lib/libglib-2.0.so.0
#5  0x00007ffff0c28075 in start_thread () at /usr/lib/libpthread.so.0
#6  0x00007ffff3c7a53f in clone () at /usr/lib/libc.so.6

Thread 23 (Thread 0x7fffacaf9700 (LWP 28565)):
#0  0x00007ffff3c750f9 in syscall () at /usr/lib/libc.so.6
#1  0x00007fffee69e411 in g_cond_wait () at /usr/lib/libglib-2.0.so.0
#2  0x00007fffc698c1cf in gst_task_func (task=0x5555569af950) at gsttask.c:317
#3  0x00007fffee680463 in  () at /usr/lib/libglib-2.0.so.0
#4  0x00007fffee67fa2a in  () at /usr/lib/libglib-2.0.so.0
#5  0x00007ffff0c28075 in start_thread () at /usr/lib/libpthread.so.0
#6  0x00007ffff3c7a53f in clone () at /usr/lib/libc.so.6

Thread 22 (Thread 0x7fffaf337700 (LWP 28564)):
#0  0x00007ffff3c750f9 in syscall () at /usr/lib/libc.so.6
#1  0x00007fffee69e411 in g_cond_wait () at /usr/lib/libglib-2.0.so.0
#2  0x00007fffc698c1cf in gst_task_func (task=0x5555569afa70) at gsttask.c:317
#3  0x00007fffee680463 in  () at /usr/lib/libglib-2.0.so.0
#4  0x00007fffee67fa2a in  () at /usr/lib/libglib-2.0.so.0
#5  0x00007ffff0c28075 in start_thread () at /usr/lib/libpthread.so.0
#6  0x00007ffff3c7a53f in clone () at /usr/lib/libc.so.6

Thread 21 (Thread 0x7fff9f7fe700 (LWP 28563)):
#0  0x00007ffff3c6ba07 in write () at /usr/lib/libc.so.6
#1  0x00007fffdd755d58 in pa_write (fd=20, buf=buf@entry=0x7fff9f7fd337, count=count@entry=1, type=0x5555569a7f28) at pulsecore/core-util.c:477
#2  0x00007fffddde499f in pa_mainloop_wakeup (m=<optimized out>) at pulse/mainloop.c:771
#3  0x00007fffddde4ac6 in mainloop_defer_enable (e=0x7fffa8006470, b=<optimized out>) at pulse/mainloop.c:261
#4  0x00007fffdddf0ca6 in pa_stream_write_ext_free (s=0x7fff94009f40, data=<optimized out>, length=2896, free_cb=free_cb@entry=0x0, free_cb_data=0x7fffbbf23040, offset=216744, seek=PA_SEEK_ABSOLUTE) at pulse/stream.c:1515
#5  0x00007fffdddf0e92 in pa_stream_write (s=<optimized out>, data=<optimized out>, length=<optimized out>, free_cb=free_cb@entry=0x0, offset=<optimized out>, seek=seek@entry=PA_SEEK_ABSOLUTE) at pulse/stream.c:1616
#6  0x00007fffc0921dfe in gst_pulseringbuffer_commit (buf=<optimized out>, sample=0x7fff9f7fd5c8, data=0x7fffa40828c0 "\201zǻ\017\fR\274\245 ", in_samples=<optimized out>, out_samples=<optimized out>, accum=0x7fff9f7fd5c0) at pulsesink.c:1670
#7  0x00007fffc4fc8323 in gst_audio_base_sink_render (bsink=0x555556973030, buf=0x7fffa00327c0) at gstaudiobasesink.c:2142
#8  0x00007fffc54b0a6e in gst_base_sink_chain_unlocked (basesink=basesink@entry=0x555556973030, obj=obj@entry=0x7fffa00327c0, is_list=is_list@entry=0, pad=<optimized out>) at gstbasesink.c:3546
#9  0x00007fffc54b1b71 in gst_base_sink_chain_main (basesink=0x555556973030, pad=<optimized out>, obj=0x7fffa00327c0, is_list=0) at gstbasesink.c:3672
#10 0x00007fffc6955b04 in gst_pad_chain_data_unchecked (data=0x7fffa00327c0, type=4112, pad=0x555556948420) at gstpad.c:4279
#11 0x00007fffc6955b04 in gst_pad_push_data (pad=pad@entry=0x555556948b10, type=type@entry=4112, data=data@entry=0x7fffa00327c0) at gstpad.c:4535
#12 0x00007fffc695e242 in gst_pad_push (pad=0x555556948b10, buffer=0x7fffa00327c0) at gstpad.c:4654
#13 0x00007fffc54bc0c1 in gst_base_transform_chain (pad=<optimized out>, parent=0x55555697b660, buffer=<optimized out>) at gstbasetransform.c:2321
#14 0x00007fffc6955b04 in gst_pad_chain_data_unchecked (data=0x7fffa00327c0, type=4112, pad=0x5555569481d0) at gstpad.c:4279
#15 0x00007fffc6955b04 in gst_pad_push_data (pad=pad@entry=0x555556949450, type=type@entry=4112, data=data@entry=0x7fffa00327c0) at gstpad.c:4535
#16 0x00007fffc695e242 in gst_pad_push (pad=0x555556949450, buffer=0x7fffa00327c0) at gstpad.c:4654
#17 0x00007fffc54bc0c1 in gst_base_transform_chain (pad=<optimized out>, parent=0x555556987380, buffer=<optimized out>) at gstbasetransform.c:2321
#18 0x00007fffc6955b04 in gst_pad_chain_data_unchecked (data=0x7fffa00327c0, type=4112, pad=0x555556949200) at gstpad.c:4279
#19 0x00007fffc6955b04 in gst_pad_push_data (pad=pad@entry=0x5555569488c0, type=type@entry=4112, data=data@entry=0x7fffa00327c0) at gstpad.c:4535
#20 0x00007fffc695e242 in gst_pad_push (pad=0x5555569488c0, buffer=0x7fffa00327c0) at gstpad.c:4654
#21 0x00007fffc54bc0c1 in gst_base_transform_chain (pad=<optimized out>, parent=0x5555569728e0, buffer=<optimized out>) at gstbasetransform.c:2321
#22 0x00007fffc6955b04 in gst_pad_chain_data_unchecked (data=0x7fffa00327c0, type=4112, pad=0x555556948670) at gstpad.c:4279
#23 0x00007fffc6955b04 in gst_pad_push_data (pad=pad@entry=0x555556948fb0, type=type@entry=4112, data=data@entry=0x7fffa00327c0) at gstpad.c:4535
#24 0x00007fffc695e242 in gst_pad_push (pad=0x555556948fb0, buffer=buffer@entry=0x7fffa00327c0) at gstpad.c:4654
#25 0x00007fffaf7fb763 in gst_queue_push_one (queue=0x555556982130) at gstqueue.c:1384
#26 0x00007fffaf7fb763 in gst_queue_loop (pad=<optimized out>) at gstqueue.c:1537
#27 0x00007fffc698bfcb in gst_task_func (task=0x5555569af5f0) at gsttask.c:332
#28 0x00007fffee680463 in  () at /usr/lib/libglib-2.0.so.0
#29 0x00007fffee67fa2a in  () at /usr/lib/libglib-2.0.so.0
#30 0x00007ffff0c28075 in start_thread () at /usr/lib/libpthread.so.0
#31 0x00007ffff3c7a53f in clone () at /usr/lib/libc.so.6

Thread 20 (Thread 0x7fffad508700 (LWP 28562)):
#0  0x00007ffff3c750f9 in syscall () at /usr/lib/libc.so.6
#1  0x00007fffee69e411 in g_cond_wait () at /usr/lib/libglib-2.0.so.0
#2  0x00007fffc54cbd0c in _gst_data_queue_wait_non_empty (queue=queue@entry=0x7fffa0007150) at gstdataqueue.c:554
#3  0x00007fffc54cd0f0 in gst_data_queue_pop (queue=0x7fffa0007150, item=item@entry=0x7fffad507d20) at gstdataqueue.c:596
#4  0x00007fffaf7f63b4 in gst_multi_queue_loop (pad=<optimized out>) at gstmultiqueue.c:1808
#5  0x00007fffc698bfcb in gst_task_func (task=0x7fffa0020dd0) at gsttask.c:332
#6  0x00007fffee680463 in  () at /usr/lib/libglib-2.0.so.0
#7  0x00007fffee67fa2a in  () at /usr/lib/libglib-2.0.so.0
#8  0x00007ffff0c28075 in start_thread () at /usr/lib/libpthread.so.0
#9  0x00007ffff3c7a53f in clone () at /usr/lib/libc.so.6

Thread 19 (Thread 0x7fffadd09700 (LWP 28561)):
#0  0x00007ffff3c750f9 in syscall () at /usr/lib/libc.so.6
#1  0x00007fffee69e411 in g_cond_wait () at /usr/lib/libglib-2.0.so.0
#2  0x00007fffc698c1cf in gst_task_func (task=0x7fffa0020950) at gsttask.c:317
#3  0x00007fffee680463 in  () at /usr/lib/libglib-2.0.so.0
#4  0x00007fffee67fa2a in  () at /usr/lib/libglib-2.0.so.0
#5  0x00007ffff0c28075 in start_thread () at /usr/lib/libpthread.so.0
#6  0x00007ffff3c7a53f in clone () at /usr/lib/libc.so.6

Thread 18 (Thread 0x7fffccbdd700 (LWP 28560)):
#0  0x00007ffff0c2a2b0 in __pthread_mutex_lock_full () at /usr/lib/libpthread.so.0
#1  0x00007fffdd78509f in pa_mutex_lock (m=m@entry=0x5555569a5d20) at pulsecore/mutex-posix.c:90
#2  0x00007fffdddf474e in poll_func (ufds=<optimized out>, nfds=3, timeout=169, userdata=0x5555569a5d20) at pulse/thread-mainloop.c:70
#3  0x00007fffddde5a60 in pa_mainloop_poll (m=m@entry=0x5555569a7e50) at pulse/mainloop.c:824
#4  0x00007fffddde60b0 in pa_mainloop_iterate (m=0x5555569a7e50, block=<optimized out>, retval=0x0) at pulse/mainloop.c:926
#5  0x00007fffddde6161 in pa_mainloop_run (m=0x5555569a7e50, retval=retval@entry=0x0) at pulse/mainloop.c:945
#6  0x00007fffdddf467e in thread (userdata=0x555556970e70) at pulse/thread-mainloop.c:100
#7  0x00007fffdd785f8c in internal_thread_func (userdata=0x5555569a6ad0) at pulsecore/thread-posix.c:81
#8  0x00007ffff0c28075 in start_thread () at /usr/lib/libpthread.so.0
#9  0x00007ffff3c7a53f in clone () at /usr/lib/libc.so.6

Thread 17 (Thread 0x7fff9effd700 (LWP 28082)):
#0  0x00007ffff3c750f9 in syscall () at /usr/lib/libc.so.6
#1  0x00007fffee69e411 in g_cond_wait () at /usr/lib/libglib-2.0.so.0
#2  0x00007fffc698c1cf in gst_task_func (task=0x5555569af290) at gsttask.c:317
#3  0x00007fffee680463 in  () at /usr/lib/libglib-2.0.so.0
#4  0x00007fffee67fa2a in  () at /usr/lib/libglib-2.0.so.0
#5  0x00007ffff0c28075 in start_thread () at /usr/lib/libpthread.so.0
#6  0x00007ffff3c7a53f in clone () at /usr/lib/libc.so.6

Thread 3 (Thread 0x7fffdc0a4700 (LWP 27782)):
#0  0x00007ffff3c6fea9 in poll () at /usr/lib/libc.so.6
#1  0x00007fffee657523 in  () at /usr/lib/libglib-2.0.so.0
#2  0x00007fffee65763e in g_main_context_iteration () at /usr/lib/libglib-2.0.so.0
#3  0x00007ffff45c0231 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5
#4  0x00007ffff456231b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5
#5  0x00007ffff437171e in QThread::exec() () at /usr/lib/libQt5Core.so.5
#6  0x00007ffff49e3416 in  () at /usr/lib/libQt5DBus.so.5
#7  0x00007ffff4376abd in  () at /usr/lib/libQt5Core.so.5
#8  0x00007ffff0c28075 in start_thread () at /usr/lib/libpthread.so.0
#9  0x00007ffff3c7a53f in clone () at /usr/lib/libc.so.6

Thread 2 (Thread 0x7fffe5e5f700 (LWP 27742)):
#0  0x00007ffff3c6fea9 in poll () at /usr/lib/libc.so.6
#1  0x00007ffff104e180 in  () at /usr/lib/libxcb.so.1
#2  0x00007ffff104fe4b in xcb_wait_for_event () at /usr/lib/libxcb.so.1
#3  0x00007fffe8c0a82a in  () at /usr/lib/libQt5XcbQpa.so.5
#4  0x00007ffff4376abd in  () at /usr/lib/libQt5Core.so.5
#5  0x00007ffff0c28075 in start_thread () at /usr/lib/libpthread.so.0
#6  0x00007ffff3c7a53f in clone () at /usr/lib/libc.so.6
---Type <return> to continue, or q <return> to quit---

Thread 1 (Thread 0x7ffff7f8de80 (LWP 27699)):
#0  0x00007ffff0c2a2b0 in __pthread_mutex_lock_full () at /usr/lib/libpthread.so.0
#1  0x00007fffdd78509f in pa_mutex_lock (m=<optimized out>) at pulsecore/mutex-posix.c:90
#2  0x00007fffdddf4b2d in pa_threaded_mainloop_lock (m=<optimized out>) at pulse/thread-mainloop.c:180
#3  0x00007fffc092123d in gst_pulsesink_get_time (clock=<optimized out>, sink=<optimized out>) at pulsesink.c:2024
#4  0x00007fffc4faf5a4 in gst_audio_clock_get_internal_time (clock=0x55555694a610) at gstaudioclock.c:161
#5  0x00007fffc692b8b6 in gst_clock_get_internal_time (clock=clock@entry=0x55555694a610) at gstclock.c:1043
#6  0x00007fffc692bad9 in gst_clock_get_time (clock=clock@entry=0x55555694a610) at gstclock.c:1083
#7  0x00007fffc54a63cb in gst_base_sink_get_position (basesink=basesink@entry=0x555556973030, format=GST_FORMAT_TIME, cur=cur@entry=0x7fffffffc590, upstream=upstream@entry=0x7fffffffc58c) at gstbasesink.c:4691
#8  0x00007fffc54ad36c in default_element_query (element=0x555556973030, query=0x7fffa0004c50) at gstbasesink.c:4819
#9  0x00007fffc4fc5626 in gst_audio_base_sink_query (element=0x555556973030, query=0x7fffa0004c50) at gstaudiobasesink.c:502
#10 0x00007fffc693afb5 in gst_element_query (element=element@entry=0x555556973030, query=0x7fffa0004c50) at gstelement.c:1963
#11 0x00007fffc6911e15 in bin_query_position_fold (vitem=<optimized out>, ret=0x7fffffffc740, fold=0x7fffffffc7d0) at gstbin.c:4141
#12 0x00007fffc694a88c in gst_iterator_fold (it=it@entry=0x5555569c6160, func=func@entry=0x7fffc6911d80 <bin_query_position_fold>, ret=ret@entry=0x7fffffffc740, user_data=user_data@entry=0x7fffffffc7d0) at gstiterator.c:617
#13 0x00007fffc6912055 in bin_iterate_fold (bin=bin@entry=0x555556971110, iter=iter@entry=0x5555569c6160, fold_init=fold_init@entry=0x7fffc6910b10 <bin_query_min_max_init>, fold_done=fold_done@entry=0x7fffc6914ba0 <bin_query_position_done>, fold_func=fold_func@entry=0x7fffc6911d80 <bin_query_position_fold>, fold_data=fold_data@entry=0x7fffffffc7d0, default_return=0) at gstbin.c:4258
#14 0x00007fffc6918169 in gst_bin_query (element=0x555556971110, query=0x7fffa0004c50) at gstbin.c:4378
#15 0x00007fffc693afb5 in gst_element_query (element=element@entry=0x555556971110, query=0x7fffa0004c50) at gstelement.c:1963
#16 0x00007fffc6911e15 in bin_query_position_fold (vitem=<optimized out>, ret=0x7fffffffc920, fold=0x7fffffffc9b0) at gstbin.c:4141
#17 0x00007fffc694a88c in gst_iterator_fold (it=it@entry=0x5555569c60b0, func=func@entry=0x7fffc6911d80 <bin_query_position_fold>, ret=ret@entry=0x7fffffffc920, user_data=user_data@entry=0x7fffffffc9b0) at gstiterator.c:617
#18 0x00007fffc6912055 in bin_iterate_fold (bin=bin@entry=0x5555569712b0, iter=iter@entry=0x5555569c60b0, fold_init=fold_init@entry=0x7fffc6910b10 <bin_query_min_max_init>, fold_done=fold_done@entry=0x7fffc6914ba0 <bin_query_position_done>, fold_func=fold_func@entry=0x7fffc6911d80 <bin_query_position_fold>, fold_data=fold_data@entry=0x7fffffffc9b0, default_return=0) at gstbin.c:4258
#19 0x00007fffc6918169 in gst_bin_query (element=0x5555569712b0, query=0x7fffa0004c50) at gstbin.c:4378
#20 0x00007fffc693afb5 in gst_element_query (element=element@entry=0x5555569712b0, query=0x7fffa0004c50) at gstelement.c:1963
#21 0x00007fffc6911e15 in bin_query_position_fold (vitem=<optimized out>, ret=0x7fffffffcb00, fold=0x7fffffffcb90) at gstbin.c:4141
#22 0x00007fffc694a88c in gst_iterator_fold (it=it@entry=0x7fff88007e40, func=func@entry=0x7fffc6911d80 <bin_query_position_fold>, ret=ret@entry=0x7fffffffcb00, user_data=user_data@entry=0x7fffffffcb90) at gstiterator.c:617
#23 0x00007fffc6912055 in bin_iterate_fold (bin=bin@entry=0x555556971790, iter=iter@entry=0x7fff88007e40, fold_init=fold_init@entry=0x7fffc6910b10 <bin_query_min_max_init>, fold_done=fold_done@entry=0x7fffc6914ba0 <bin_query_position_done>, fold_func=fold_func@entry=0x7fffc6911d80 <bin_query_position_fold>, fold_data=fold_data@entry=0x7fffffffcb90, default_return=0) at gstbin.c:4258
#24 0x00007fffc6918169 in gst_bin_query (element=0x555556971790, query=0x7fffa0004c50) at gstbin.c:4378
#25 0x00007fffc693afb5 in gst_element_query (element=element@entry=0x555556971790, query=0x7fffa0004c50) at gstelement.c:1963
#26 0x00007fffc6911e15 in bin_query_position_fold (vitem=<optimized out>, ret=0x7fffffffcce0, fold=0x7fffffffcd70) at gstbin.c:4141
#27 0x00007fffc694a88c in gst_iterator_fold (it=it@entry=0x5555569c6420, func=func@entry=0x7fffc6911d80 <bin_query_position_fold>, ret=ret@entry=0x7fffffffcce0, user_data=user_data@entry=0x7fffffffcd70) at gstiterator.c:617
#28 0x00007fffc6912055 in bin_iterate_fold (bin=bin@entry=0x55555699a1f0, iter=iter@entry=0x5555569c6420, fold_init=fold_init@entry=0x7fffc6910b10 <bin_query_min_max_init>, fold_done=fold_done@entry=0x7fffc6914ba0 <bin_query_position_done>, fold_func=fold_func@entry=0x7fffc6911d80 <bin_query_position_fold>, fold_data=fold_data@entry=0x7fffffffcd70, default_return=0) at gstbin.c:4258
#29 0x00007fffc6918169 in gst_bin_query (element=0x55555699a1f0, query=0x7fffa0004c50) at gstbin.c:4378
#30 0x00007fffc693afb5 in gst_element_query (element=element@entry=0x55555699a1f0, query=0x7fffa0004c50) at gstelement.c:1963
#31 0x00007fffc6911e15 in bin_query_position_fold (vitem=<optimized out>, ret=0x7fffffffcec0, fold=0x7fffffffcf50) at gstbin.c:4141
#32 0x00007fffc694a88c in gst_iterator_fold (it=it@entry=0x5555569c6000, func=func@entry=0x7fffc6911d80 <bin_query_position_fold>, ret=ret@entry=0x7fffffffcec0, user_data=user_data@entry=0x7fffffffcf50) at gstiterator.c:617
#33 0x00007fffc6912055 in bin_iterate_fold (bin=bin@entry=0x555556995e30, iter=iter@entry=0x5555569c6000, fold_init=fold_init@entry=0x7fffc6910b10 <bin_query_min_max_init>, fold_done=fold_done@entry=0x7fffc6914ba0 <bin_query_position_done>, fold_func=fold_func@entry=0x7fffc6911d80 <bin_query_position_fold>, fold_data=fold_data@entry=0x7fffffffcf50, default_return=0) at gstbin.c:4258
#34 0x00007fffc6918169 in gst_bin_query (element=0x555556995e30, query=0x7fffa0004c50) at gstbin.c:4378
#35 0x00007fffaf372cce in  () at /usr/lib/gstreamer-1.0/libgstplayback.so
#36 0x00007fffc693afb5 in gst_element_query (element=element@entry=0x555556995e30, query=query@entry=0x7fffa0004c50) at gstelement.c:1963
#37 0x00007fffc6996d6f in gst_element_query_position (element=0x555556995e30, format=<optimized out>, cur=0x7fffffffd070) at gstutils.c:2435
#38 0x00007fffc6c5f6a1 in  () at /usr/lib/qt5/plugins/phonon4qt5_backend/phonon_gstreamer.so
#39 0x00007fffc6c5053f in  () at /usr/lib/qt5/plugins/phonon4qt5_backend/phonon_gstreamer.so
#40 0x00007fffc6c5449f in  () at /usr/lib/qt5/plugins/phonon4qt5_backend/phonon_gstreamer.so
#41 0x00007ffff4594606 in QMetaObject::activate(QObject*, int, int, void**) () at /usr/lib/libQt5Core.so.5
#42 0x00007ffff45a14f8 in QTimer::timeout(QTimer::QPrivateSignal) () at /usr/lib/libQt5Core.so.5
#43 0x00007ffff45a1869 in QTimer::timerEvent(QTimerEvent*) () at /usr/lib/libQt5Core.so.5
#44 0x00007ffff459500b in QObject::event(QEvent*) () at /usr/lib/libQt5Core.so.5
#45 0x00007ffff5802fec in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib/libQt5Widgets.so.5
#46 0x00007ffff580a9c6 in QApplication::notify(QObject*, QEvent*) () at /usr/lib/libQt5Widgets.so.5
#47 0x00007ffff4563ce0 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /usr/lib/libQt5Core.so.5
#48 0x00007ffff45bf678 in QTimerInfoList::activateTimers() () at /usr/lib/libQt5Core.so.5
#49 0x00007ffff45bfe72 in  () at /usr/lib/libQt5Core.so.5
#50 0x00007fffee657368 in g_main_context_dispatch () at /usr/lib/libglib-2.0.so.0
#51 0x00007fffee6575b1 in  () at /usr/lib/libglib-2.0.so.0
#52 0x00007fffee65763e in g_main_context_iteration () at /usr/lib/libglib-2.0.so.0
#53 0x00007ffff45c0231 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5
#54 0x00007fffe8c92482 in  () at /usr/lib/libQt5XcbQpa.so.5
#55 0x00007ffff456231b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5
#56 0x00007ffff59fa69b in QDialog::exec() () at /usr/lib/libQt5Widgets.so.5
#57 0x00007ffff68e1006 in KMessageBox::createKMessageBox(QDialog*, QDialogButtonBox*, QIcon const&, QString const&, QStringList const&, QString const&, bool*, QFlags<KMessageBox::Option>, QString const&, QMessageBox::Icon) () at /usr/lib/libKF5WidgetsAddons.so.5
#58 0x00007ffff68e149d in KMessageBox::createKMessageBox(QDialog*, QDialogButtonBox*, QMessageBox::Icon, QString const&, QStringList const&, QString const&, bool*, QFlags<KMessageBox::Option>, QString const&) () at /usr/lib/libKF5WidgetsAddons.so.5
#59 0x00007ffff68e4fb6 in  () at /usr/lib/libKF5WidgetsAddons.so.5
#60 0x00007ffff68e51e5 in KMessageBox::information(QWidget*, QString const&, QString const&, QString const&, QFlags<KMessageBox::Option>) () at /usr/lib/libKF5WidgetsAddons.so.5
#61 0x00007fffda9eab85 in  () at /usr/lib/qt/plugins/okularpart.so
#62 0x00007ffff45a15a4 in  () at /usr/lib/libQt5Core.so.5
#63 0x00007ffff459500b in QObject::event(QEvent*) () at /usr/lib/libQt5Core.so.5
#64 0x00007ffff5802fec in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib/libQt5Widgets.so.5
#65 0x00007ffff580a9c6 in QApplication::notify(QObject*, QEvent*) () at /usr/lib/libQt5Widgets.so.5
#66 0x00007ffff4563ce0 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /usr/lib/libQt5Core.so.5
#67 0x00007ffff45bf678 in QTimerInfoList::activateTimers() () at /usr/lib/libQt5Core.so.5
#68 0x00007ffff45bfe72 in  () at /usr/lib/libQt5Core.so.5
#69 0x00007fffee657368 in g_main_context_dispatch () at /usr/lib/libglib-2.0.so.0
#70 0x00007fffee6575b1 in  () at /usr/lib/libglib-2.0.so.0
#71 0x00007fffee65763e in g_main_context_iteration () at /usr/lib/libglib-2.0.so.0
#72 0x00007ffff45c0231 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5
#73 0x00007fffe8c92482 in  () at /usr/lib/libQt5XcbQpa.so.5
#74 0x00007ffff456231b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5
#75 0x00007ffff456b718 in QCoreApplication::exec() () at /usr/lib/libQt5Core.so.5
#76 0x000055555555f685 in  ()
#77 0x00007ffff3ba506b in __libc_start_main () at /usr/lib/libc.so.6
#78 0x0000555555560d4a in _start ()