Fix z githubu (originalni repozitar).

src/AsyncWebSocket.cpp

@@ -212,6 +212,8 @@ public:
     uint8_t opcode(){ return _opcode; }
     uint8_t len(){ return _len + 2; }
     size_t send(AsyncClient *client){
+        if (_finished)
+            return 0; // fix from https://github.com/me-no-dev/ESPAsyncWebServer/pull/1390/files
         _finished = true;
         return webSocketSendFrame(client, true, _opcode & 0x0F, _mask, _data, _len);
     }