message: Fix operator== for actor
diff: @@ -109,7 +109,7 @@ actor actor::splice_impl(std::initializer_list<actor> xs) {
  }
  bool operator==(const actor& lhs, abstract_actor* rhs) {
  - return actor_cast<abstract_actor*>(lhs) == rhs;
  + return lhs ? actor_cast<abstract_actor*>(lhs) == rhs : rhs == nullptr;
  }
  bool operator==(abstract_actor* lhs, const actor& rhs) {
  