PVS-Studio warning V547 for FCEUX

void CenterWindow(HWND hwndDlg)
{
  ...
  unsigned x = ((rectP.right-rectP.left) - width) / 2 +
               rectP.left;
  unsigned y = ((rectP.bottom-rectP.top) - height) / 2 +
               rectP.top;
  ...
  // make sure that the dialog box never moves outside
  // of the screen
  if(x < 0) x = 0;
  if(y < 0) y = 0;
  if(x + width  > screenwidth)  x = screenwidth  - width;
  if(y + height > screenheight) y = screenheight - height;
  ...
}

This suspicious code was found in FCEUX project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'x < 0' is always false. Unsigned type value is never < 0. fceux gui.cpp 32

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/