handle non-dict connection error data for On Air

nicegui/air.py

@@ -171,7 +171,8 @@ class Air:
 
         @self.relay.on('connect_error')
         async def _handle_connect_error(data) -> None:
-            self.log.warning(f'Connection error: {data.get("message", "Unknown error")}')
+            message = data.get('message', 'Unknown error') if isinstance(data, dict) else data
+            self.log.warning(f'Connection error: {message}')
 
         @self.relay.on('event')
         def _handle_event(data: Dict[str, Any]) -> None: