PVS-Studio warning V547 for SeqAn

template <typename TStream, typename TPass, typename TBuffer>
inline int
readLineStripTrailingBlanks(TBuffer & buffer,
  RecordReader<TStream, TPass> & reader)
{
  ....
  typename Size<TBuffer>::Type pos = length(buffer) - 1;

  if (pos < 0)
    return 0;
  ....
}

This suspicious code was found in SeqAn project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'pos < 0' is always false. Unsigned type value is never < 0. tokenize.h 1548

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