outposts: fix error on outpost disconnect

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

authentik/outposts/channels.py

@@ -65,6 +65,7 @@ class OutpostConsumer(AuthJsonConsumer):
     def disconnect(self, close_code):
         if self.outpost and self.last_uid:
             state = OutpostState.for_instance_uid(self.outpost, self.last_uid)
+            if self.channel_name in state.channel_ids:
                 state.channel_ids.remove(self.channel_name)
                 state.save()
         LOGGER.debug(