message: Cleanup link state in blocking actors, close
diff: @@ -353,6 +353,9 @@ void blocking_actor::receive_impl(receive_cond& rcc,
  skipped = true;
  CAF_LOG_SKIP_EVENT();
  } else {
  + // automatically unlink from actors when receiving exit messages
  + if (x.content().match_elements<exit_msg>())
  + unlink_from(x.content().get_as<exit_msg>(0).source);
  // blocking actors can use nested receives => restore current_element_
  auto prev_element = current_element_;
  current_element_ = &x;
  