message: Server->task check null.
diff: @@ -3738,7 +3738,7 @@ static PHP_METHOD(swoole_server, task)
  Z_PARAM_ZVAL(data)
  Z_PARAM_OPTIONAL
  Z_PARAM_LONG(dst_worker_id)
  - Z_PARAM_ZVAL(callback)
  + Z_PARAM_ZVAL_EX(callback, 1, 0)
  ZEND_PARSE_PARAMETERS_END_EX(RETURN_FALSE);
  if (php_swoole_check_task_param(serv, dst_worker_id) < 0)
  