chore: do not try to disconnect ws if not connected

cf https://umap.sentry.io/issues/6331841272/

umap/sync/app.py

@@ -112,6 +112,7 @@ class Peer:
         self.client = redis.from_url(settings.REDIS_URL)
 
     async def disconnect(self):
+        if self.is_authenticated:
             await self.client.hdel(self.room_key, self.peer_id)
             for pubsub in self._subscriptions:
                 await pubsub.unsubscribe()