message: Fix memory leak in unit test
diff: @@ -88,8 +88,6 @@ public:
  struct send_helper {
  app_t* thisptr;
  LowerLayerPtr down;
  - bool on_next_called;
  - bool aborted;
  void on_next(int32_t item) {
  thisptr->written_values.emplace_back(item);
  @@ -109,19 +107,20 @@ public:
  }
  void on_error(const error&) {
  - aborted = true;
  + // nop
  }
  };
  template <class LowerLayerPtr>
  bool prepare_send(LowerLayerPtr down) {
  - if (done)
  + if (done || !adapter)
  return true;
  - auto helper = send_helper<LowerLayerPtr>{this, down, false, false};
  + auto helper = send_helper<LowerLayerPtr>{this, down};
  while (down->can_send_more()) {
  - auto [ok, consumed] = adapter->pull(async::delay_errors, 1, helper);
  - if (!ok) {
  + auto [again, consumed] = adapter->pull(async::delay_errors, 1, helper);
  + if (!again) {
  MESSAGE("adapter signaled end-of-buffer");
  + adapter = nullptr;
  done = true;
  break;
  } else if (consumed == 0) {
  