#vulnerable code 
                              @Override
  public ScreenImage capture(Rectangle rect) {
    Debug.log(3, "ScreenUnion: capture: " + rect);
    return Region.create(rect).getScreen().capture(rect);
  } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                              @Override
  public ScreenImage capture(Rectangle rect) {
    Debug.log(3, "ScreenUnion: capture: " + rect);
    Screen s = Screen.getPrimaryScreen();
    Location tl = new Location(rect.getLocation());
    for (Screen sx : Screen.screens) {
      if (sx.contains(tl)) {
        s = sx;
        break;
      }
    }
    ScreenImage si = s.capture(rect);
    return si;
  }