plugin-account.c: unique_name(): don't crash if 'account' is not a string
plugin-account.c: unique_name(): don't crash if 'account' is not a string

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