#vulnerable code 
                                @Test
    public void shutdown() throws Exception {
        Client client = TestGraphUtil.instance.createClient();
        client.delegate().shutdown();
    } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void shutdown() throws Exception {
        Client client = TestGraphUtil.instance.createClient();
        client.getDelegate().shutdown();
    }