message: Keep actors alive that still have stream managers
diff: @@ -671,7 +671,9 @@ public:
  inline bool has_behavior() const {
  return !bhvr_stack_.empty()
  || !awaited_responses_.empty()
  - || !multiplexed_responses_.empty();
  + || !multiplexed_responses_.empty()
  + || !stream_managers_.empty()
  + || !pending_stream_managers_.empty();
  }
  inline behavior& current_behavior() {
  