fix(WebSocketShard): only cleanup the connection if a connection still exists (#8946)

fix(WebSocketShard): only cleanup if connection

packages/discord.js/src/client/websocket/WebSocketShard.js

@@ -603,7 +603,9 @@ class WebSocketShard extends EventEmitter {
       );
 
       // Cleanup connection listeners
-      this._cleanupConnection();
+      if (this.connection) {
+        this._cleanupConnection();
+      }
 
       this.emitClose();
       // Setting the variable false to check for zombie connections.