PVS-Studio warning V547 for TortoiseGIT

void CCloneDlg::OnBnClickedCheckSvn()
{
  ....
  CString str;
  m_URLCombo.GetWindowText(str);

  while(str.GetLength()>=1 &&
        str[str.GetLength()-1] == _T('\\') &&
        str[str.GetLength()-1] == _T('/'))
  {
    str=str.Left(str.GetLength()-1);
  }
  ....
}

This suspicious code was found in TortoiseGIT project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression is always false. Probably the '||' operator should be used here. clonedlg.cpp 413

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/