#fixed code
                                @Before
    public void setUp() throws Exception {
        String content = File2String.read("appmsg-file.xml");
        WechatMessage m = new WechatMessage();
        m.Content = content;
        handler = new AppMsgXmlHandler(m);
    }
#vulnerable code 
                                @Before
    public void setUp() throws Exception {
        String content = File2String.read("appmsg-file.xml");
        handler = new AppMsgXmlHandler(content);
    } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE