fix room cleanup for non-notebooks

Author: dlqqq

jupyter_server_documents/rooms/yroom_manager.py

@@ -182,7 +182,7 @@ async def _watch_rooms(self) -> None:
                 # cells, so the room should not be closed.
                 awareness = room.get_awareness().get_local_state() or {}
                 execution_state = awareness.get("kernel", {}).get("execution_state", None)
-                if execution_state not in { "idle", "dead" }:
+                if execution_state not in { "idle", "dead", None }:
                     continue
 
                 # Otherwise, delete the room