PVS-Studio warning V547 for Virtualdub

void VDVideoCompressorVCM::GetState(vdfastvector<uint8>& data) {
  DWORD res;
  ....
  res = ICGetState(hic, data.data(), size);
  ....
  if (res < 0)
    throw MyICError("Video compression", res);
}

This suspicious code was found in Virtualdub project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'res < 0' is always false. Unsigned type value is never < 0. Riza w32videocodecpack.cpp 828

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/