PVS-Studio warning V669 for WinMerge

bool CDirView::OpenOneItem(
  UINT_PTR pos1, DIFFITEM **di1, DIFFITEM **di2,
  String &path1, String &path2, int & sel1, bool & isDir)
{
  ....
  // Variable 'sel1' don't modified.
  ....
}

This suspicious code was found in WinMerge project by PVS-Studio static code analyzer.
Warning message is:
V669 The 'sel1' argument is a non-constant reference. The analyzer is unable to determine the position at which this argument is being modified. It is possible that the function contains an error. dirview.cpp 1322

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/