[BugFix] Fix async core engine client finalizer (#24540)

Signed-off-by: Nick Hill <nhill@redhat.com>

vllm/v1/engine/core_client.py

@@ -347,8 +347,9 @@ class BackgroundResources:
 
         if isinstance(self.output_socket, zmq.asyncio.Socket):
             # Async case.
-            loop = self.output_socket._get_loop()
-            asyncio.get_running_loop()
+            loop = self.output_queue_task._loop \
+                if self.output_queue_task else None
+
             sockets = (self.output_socket, self.input_socket,
                        self.first_req_send_socket, self.first_req_rcv_socket,
                        self.stats_update_socket)
@@ -359,11 +360,12 @@ class BackgroundResources:
                 close_sockets(sockets)
                 for task in tasks:
                     if task is not None and not task.done():
+                        with contextlib.suppress(Exception):
                             task.cancel()
 
             if in_loop(loop):
                 close_sockets_and_tasks()
-            elif not loop.is_closed():
+            elif loop and not loop.is_closed():
                 loop.call_soon_threadsafe(close_sockets_and_tasks)
             else:
                 # Loop has been closed, try to clean up directly.