Make sure the channel list is always consistent
Make sure the channel list is always consistent

Move the mcd_operation_get_missions() call inside the loop, because
mcd_dispatcher_send() can cause the channel to be destroyed, and when that
happened our list contained a finalized channel (and a crash did happen)

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