message: protecting core
diff: @@ -158,6 +158,10 @@ void Coroutine::bailout(sw_coro_bailout_t func)
  {
  co = co->origin;
  }
  + if (!co->task)
  + {
  + exit(255);
  + }
  // it will jump to main context directly (it also breaks contexts)
  co->yield();
  // expect that never here
  