PVS-Studio warning V547 for TortoiseSVN

CString CPathUtils::PathUnescape (const char* path)
{
  // try quick path
  size_t i = 0;
  for (; char c = path[i]; ++i)
    if ((c >= 0x80) || (c == '%'))
    {
      // quick path does not work for
      // non-latin or escaped chars
      std::string utf8Path (path);
      CPathUtils::Unescape (&utf8Path[0]);
      return CUnicodeUtils::UTF8ToUTF16 (utf8Path);
    }
  ...
}

This suspicious code was found in TortoiseSVN project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'c >= 0x80' is always false. The value range of signed char type: [-128, 127]. pathutils.cpp 559

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