#vulnerable code 
                              @Override
  public void update(EventSubject es) {
    OverlayCapturePrompt cp = null;
    ScreenImage simg = cp.getSelection();
    Screen.closePrompt();
    if (simg != null) {
      try {
        Thread.sleep(300);
      } catch (InterruptedException ie) {
      }
      Rectangle roi = simg.getROI();
      pyText = String.format("%d,%d,%d,%d",
              (int) roi.x, (int) roi.y, (int) roi.width, (int) roi.height);
      setText(pyText);
      pyText = "Region(" + pyText + ")";
    }
    Screen.resetPrompt(cp);
    SikuliIDE.getInstance().setVisible(true);
  } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                              @Override
  public void update(EventSubject es) {
    OverlayCapturePrompt ocp = (OverlayCapturePrompt) es;
    ScreenImage simg = ocp.getSelection();
    Screen.closePrompt();
    if (simg != null) {
      try {
        Thread.sleep(300);
      } catch (InterruptedException ie) {
      }
      Rectangle roi = simg.getROI();
      pyText = String.format("%d,%d,%d,%d",
              (int) roi.x, (int) roi.y, (int) roi.width, (int) roi.height);
      setText(pyText);
      pyText = "Region(" + pyText + ")";
    }
    Screen.resetPrompt(ocp);
    SikuliIDE.showAgain();
  }