PVS-Studio warning V655 for Scilab

int sci_displaytree(char *fname, unsigned long fname_len)
{
  ....
  string szCurLevel = "";
  ....
  //Add node level
  if (szCurLevel != "")
  {
    szCurLevel + ".";
  }
  ....
}

This suspicious code was found in Scilab project by PVS-Studio static code analyzer.
Warning message is:
V655 The strings was concatenated but are not utilized. Consider inspecting the 'szCurLevel + "."' expression. sci_displaytree.cpp 80

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