message: Prevent redundant upstream messages
diff: @@ -55,7 +55,11 @@ void stream_manager::handle(inbound_path*, downstream_msg::close&) {
  // nop
  }
  -void stream_manager::handle(inbound_path*, downstream_msg::forced_close& x) {
  +void stream_manager::handle(inbound_path* in, downstream_msg::forced_close& x) {
  + CAF_ASSERT(in != nullptr);
  + CAF_LOG_TRACE(CAF_ARG2("slots", in->slots) << CAF_ARG(x));
  + // Reset the actor handle to make sure no further message travels upstream.
  + in->hdl = nullptr;
  abort(std::move(x.reason));
  }
  