fix: error on heartbeat

Signed-off-by: Ricardo Arturo Cabral Mejía <me@ricardocabral.io>

src/adapters/web-socket-server-adapter.ts

@@ -101,7 +101,9 @@ export class WebSocketServerAdapter extends WebServerAdapter implements IWebSock
   private onHeartbeat() {
     this.webSocketServer.clients.forEach((webSocket) => {
       const webSocketAdapter = this.webSocketsAdapters.get(webSocket) as IWebSocketAdapter
+      if (webSocketAdapter) {
         webSocketAdapter.emit(WebSocketAdapterEvent.Heartbeat)
+      }
     })
   }
 }