fix NULL ptr when server abort the connection (Links2004#207)

Author: Links2004

src/WebSocketsClient.cpp

@@ -616,14 +616,16 @@ void WebSocketsClient::handleHeader(WSclient_t * client, String * headerLine) {
 
  runCbEvent(WStype_CONNECTED, (uint8_t *) client->cUrl.c_str(), client->cUrl.length());
 
- } else if(clientIsConnected(client) && client->isSocketIO && client->cSessionId.length() > 0) {
- sendHeader(client);
- } else {
- DEBUG_WEBSOCKETS("[WS-Client][handleHeader] no Websocket connection close.\n");
- client->tcp->write("This is a webSocket client!");
- clientDisconnect(client);
- }
- }
+} else if(clientIsConnected(client) && client->isSocketIO && client->cSessionId.length() > 0) {
+sendHeader(client);
+} else {
+DEBUG_WEBSOCKETS("[WS-Client][handleHeader] no Websocket connection close.\n");
+if(clientIsConnected(client)) {
+client->tcp->write("This is a webSocket client!");
+}
+clientDisconnect(client);
+}
+}
 }
 
 void WebSocketsClient::connectedCb() {