PVS-Studio warning V547 for TPP

double SpectraSTPeakList::calcXCorr() {
  ....
  for (int tau = -75; tau <= 75; tau++) {

    float dot = 0.0;
    for (unsigned int b = 0; b < numBins; b++) {
      if (b + tau >= 0 && b + tau < (int)numBins) {
        dot += (*m_bins)[b] * theoBins[b + tau] / 10000.0;
      }
    }
    ....
  ....
}

This suspicious code was found in TPP project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'b + tau >= 0' is always true. Unsigned type value is always >= 0. spectrastpeaklist.cpp 2058

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