message: Fix invocation order
diff: @@ -181,12 +181,12 @@ private:
  void deliver(uint32_t n) {
  auto first = buf_ + rd_pos_;
  auto last = first + n;
  - sink_.on_next(span<const T>{first, n});
  - std::destroy(first, last);
  CAF_ASSERT(rd_pos_ + n <= wr_pos_);
  rd_pos_ += n;
  CAF_ASSERT(credit_ >= n);
  credit_ -= n;
  + sink_.on_next(span<const T>{first, n});
  + std::destroy(first, last);
  }
  void shift_elements() {
  