gibber-oob-file-transfer: disconnect the channel watcher when disposing so input_channel_readable_cb isn't called after object disposing
gibber-oob-file-transfer: disconnect the channel watcher when disposing so input_channel_readable_cb isn't called after object disposing

freedesktop-unofficial-mirror/telepathy__telepathy-salut,freedesktop-unofficial-mirror/telepathy__telepathy-salut,freedesktop-unofficial-mirror/telepathy__telepathy-salut,freedesktop-unofficial-mirror/telepathy__telepathy-salut