message: fix the Segmentation fault
diff: @@ -260,6 +260,12 @@ static PHP_METHOD(swoole_coroutine_scheduler, start)
  }
  php_swoole_reactor_init();
  s->started = true;
  +
  + if (!s->list) {
  + php_swoole_fatal_error(E_ERROR, "no coroutine task");
  + RETURN_FALSE;
  + }
  +
  while (!s->list->empty())
  {
  scheduler_task_t *task = s->list->front();
  