message: Fix null-pointer check, close
diff: @@ -78,8 +78,8 @@ behavior pong(event_based_actor* self, suite_state_ptr ssp) {
  behavior peer_fun(broker* self, connection_handle hdl, const actor& buddy) {
  CAF_MESSAGE("peer_fun called");
  + CAF_REQUIRE(self != nullptr);
  CAF_REQUIRE(self->subtype() == resumable::io_actor);
  - CAF_CHECK(self != nullptr);
  self->monitor(buddy);
  self->set_down_handler([self](down_msg& dm) {
  // Stop if buddy is done.
  