PVS-Studio warning V547 for TortoiseSVN

BOOL TortoiseBlame::OpenFile(const TCHAR *fileName)
{
  ...
  // check each line for illegal utf8 sequences.
  // If one is found, we treat
  // the file as ASCII, otherwise we assume
  // an UTF8 file.
  char * utf8CheckBuf = lineptr;
  while ((bUTF8)&&(*utf8CheckBuf))
  {
    if ((*utf8CheckBuf == 0xC0)||
        (*utf8CheckBuf == 0xC1)||
        (*utf8CheckBuf >= 0xF5))
    {
      bUTF8 = false;
      break;
    }

   ...
  }
  ...
}

This suspicious code was found in TortoiseSVN project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression '* utf8CheckBuf == 0xC0' is always false. The value range of signed char type: [-128, 127]. tortoiseblame.cpp 310

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