message: Update websocket_server::push, allow to send empty packet.
diff: @@ -397,11 +397,6 @@ static PHP_METHOD(swoole_websocket_server, push)
  {
  RETURN_FALSE;
  }
  - else if (length == 0)
  - {
  - php_error_docref(NULL TSRMLS_CC, E_WARNING, "data is empty.");
  - RETURN_FALSE;
  - }
  swConnection *conn = swWorker_get_connection(SwooleG.serv, fd);
  if (!conn || conn->websocket_status < WEBSOCKET_STATUS_HANDSHAKE)
  