PVS-Studio warning V637 for OpenCV

void KeyPointsFilter::retainBest(
  vector<KeyPoint>& keypoints, int n_points)
{
  ....
  if( n_points > 0 && keypoints.size() > (size_t)n_points )
  {
    if (n_points==0)
    {
      keypoints.clear();
      return;
    }
  ....
}

This suspicious code was found in OpenCV project by PVS-Studio static code analyzer.
Warning message is:
V637 Two opposite conditions were encountered. The second condition is always false. Check lines: 195, 197. keypoint.cpp 195

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/