#fixed code
                              @Override
  public Response handle() throws Exception {
    waitForPageToLoad();

    int implicitWait = (Integer) getConf("implicit_wait", 0);
    long deadline = System.currentTimeMillis() + implicitWait;
    List<RemoteWebElement> elements = null;
    do {
      try {
        elements = findElements();
        if (elements.size() != 0) {
          break;
        }
      } catch (NoSuchElementException e) {
        //ignore.
      } catch (RemoteExceptionException e2) {
        // ignore.
        // if the page is reloading, the previous nodeId won't be there anymore, resulting in a
        // RemoteExceptionException: Could not find node with given id.Keep looking.
      }
    } while (System.currentTimeMillis() < deadline);

    JSONArray array = new JSONArray();

    List<JSONObject> list = new ArrayList<JSONObject>();
    for (RemoteWebElement el : elements) {
      list.add(new JSONObject().put("ELEMENT", "" + el.getNodeId().getId()));
    }

    Response resp = new Response();
    resp.setSessionId(getSession().getSessionId());
    resp.setStatus(0);
    resp.setValue(list);
    return resp;
  }
#vulnerable code 
                              @Override
  public Response handle() throws Exception {
    JSONObject payload = getRequest().getPayload();
    String type = payload.getString("using");
    String value = payload.getString("value");

    RemoteWebElement element = null;

    if (getRequest().hasVariable(":reference")) {
      int id = Integer.parseInt(getRequest().getVariableValue(":reference"));
      element = new RemoteWebElement(new NodeId(id), getSession());
    } else {
      element = getSession().getWebInspector().getDocument();
    }

    List<RemoteWebElement> res;
    if ("link text".equals(type)) {
      res = element.findElementsByLinkText(value, false);
    } else if ("partial link text".equals(type)) {
      res = element.findElementsByLinkText(value, true);
    } else if ("xpath".equals(type)) {
      res = element.findElementsByXpath(value);
    } else {
      String cssSelector = ToCSSSelectorConvertor.convertToCSSSelector(type, value);
      res = element.findElementsByCSSSelector(cssSelector);
    }

    JSONArray array = new JSONArray();

    List<JSONObject> list = new ArrayList<JSONObject>();
    for (RemoteWebElement el : res) {
      list.add(new JSONObject().put("ELEMENT", "" + el.getNodeId().getId()));
    }

    Response resp = new Response();
    resp.setSessionId(getSession().getSessionId());
    resp.setStatus(0);
    resp.setValue(list);
    return resp;
  } 
                            #location 13 
                            #vulnerability type NULL_DEREFERENCE