find_matching_channel_requests is used to figure out which requests are
satisfied or failed by TpChannelFactoryIface::new-channel and
::channel-error, respectively. But, in a pathological connection manager
where channels with the same ChannelType, TargetHandleType and
TargetHandle are sometimes managed by a TpChannelManager and other times
by a TpChannelFactoryIface, if the Factory signals something with that
CT, THT and TH first then the ChannelRequest known to the Manager will
be returned by find_matching_channel_requests. It will then be
prematurely answered and freed; when the Manager signals that token,
tp-glib will crash.

Being in this situation in the first place is insane, though.