message: Re-order frees here
diff: @@ -255,10 +255,10 @@ shared_ptr<BlockHandle> BufferManager::ConvertToPersistent(BlockManager &block_m
  new_block->buffer = make_unique<Block>(*old_block->buffer, block_id);
  // clear the old buffer and unload it
  - old_handle.reset();
  old_block->buffer.reset();
  old_block->state = BlockState::BLOCK_UNLOADED;
  old_block->memory_usage = 0;
  + old_handle.reset();
  old_block.reset();
  // persist the new block to disk
  