McdDispatchOperation: don't leak lost channels if they have not been signalled at dispose time
McdDispatchOperation: don't leak lost channels if they have not been signalled at dispose time

This shouldn't ever happen, though.

freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control