PVS-Studio warning V530 for WinMerge

/**
* @brief Get the file names on both sides for specified item.
* @note Return empty strings if item is special item.
*/
void CDirView::GetItemFileNames(int sel,
  String& strLeft, String& strRight) const
{
  UINT_PTR diffpos = GetItemKey(sel);
  if (diffpos == (UINT_PTR)SPECIAL_ITEM_POS)
  {
    strLeft.empty();
    strRight.empty();
  }
  else
  {
     ...
  }
}

This is what should have been written here: strLeft.clear(); strRight.clear();

This suspicious code was found in WinMerge project by PVS-Studio static code analyzer.
Warning message is:
V530 The return value of function 'empty' is required to be utilized

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/