Fix WS error when switching from settings to traffic viewer (#985)

ui-common/src/components/TrafficViewer/TrafficViewer.tsx

@@ -201,7 +201,9 @@ export const TrafficViewer: React.FC<TrafficViewerProps> = ({
 
   useEffect(() => {
     return () => {
+      if (ws?.current?.readyState === WebSocket.OPEN) {
         ws.current.close();
+      }
     };
   }, []);