Original bug report: https://bugzilla.gnome.org/show_bug.cgi?id=680828

I experience this crash a couple of time in Empathy (linked on libzg 0.3.19).

#0  0x00007ffff40771e9 in g_logv (log_domain=0x7ffff43ac350 "GLib-GObject", log_level=G_LOG_LEVEL_WARNING, 
    format=0x7ffff43adae0 "invalid uninstantiatable type `%s' in cast to `%s'", args1=0x7fffffffd288) at gmessages.c:758
#1  0x00007ffff40772dd in g_log (log_domain=0x7ffff43ac350 "GLib-GObject", log_level=G_LOG_LEVEL_WARNING, 
    format=0x7ffff43adae0 "invalid uninstantiatable type `%s' in cast to `%s'") at gmessages.c:792
#2  0x00007ffff439d4a3 in g_type_check_instance_cast (type_instance=0x3555480, iface_type=57191312) at gtype.c:4009
#3  0x00007ffff6dfd368 in monitor_handle_method_call (connection=0x142ac20, sender=0x7fffdc0058f0 ":1.51", 
    object_path=0x7fffdc2710f0 "/org/gnome/zeitgeist/monitor/2", interface_name=0x7fffdc007fd0 "org.gnome.zeitgeist.Monitor", 
    method_name=0x7fffdc0059a0 "NotifyInsert", parameters=0x23dbb30, invocation=0x33d1c60, user_data=0x3555480) at zeitgeist-log.c:1261
#4  0x00007ffff46b5804 in call_in_idle_cb (user_data=0x33d1c60) at gdbusconnection.c:4737
#5  0x00007ffff406fdef in g_idle_dispatch (source=0x7fffdc007d20, callback=0x7ffff46b55da <call_in_idle_cb>, user_data=0x33d1c60)
    at gmain.c:4777
#6  0x00007ffff406d7ac in g_main_dispatch (context=0x68ec60) at gmain.c:2691
#7  0x00007ffff406e35c in g_main_context_dispatch (context=0x68ec60) at gmain.c:3195
#8  0x00007ffff406e53f in g_main_context_iterate (context=0x68ec60, block=1, dispatch=1, self=0x1496e90) at gmain.c:3266
#9  0x00007ffff406e603 in g_main_context_iteration (context=0x68ec60, may_block=1) at gmain.c:3327
#10 0x00007ffff4684964 in g_application_run (application=0x6a2190, argc=1, argv=0x7fffffffd7d8) at gapplication.c:1607
#11 0x0000000000431931 in main (argc=1, argv=0x7fffffffd7d8) at empathy.c:847