message: Add missing ref
diff: @@ -209,7 +209,7 @@ public:
  private:
  // -- utility functions ------------------------------------------------------
  - static byte_buffer next_buffer_impl(buffer_cache_type cache) {
  + static byte_buffer next_buffer_impl(buffer_cache_type& cache) {
  if (cache.empty())
  return {};
  auto buf = std::move(cache.back());
  