#vulnerable code 
                                @Test
    public void cannotSearchAfterDeletingIndexes() {
        User user = new User();
        user.setAge(88);
        JOhm.save(user);

        user.setAge(77); // younger
        JOhm.save(user);

        user.setAge(66); // younger still
        JOhm.save(user);

        int id = user.getId();

        assertNotNull(JOhm.get(User.class, id));

        List<User> users = JOhm.find(User.class, "age", 88);
        assertEquals(0, users.size()); // index already updated
        users = JOhm.find(User.class, "age", 77);
        assertEquals(0, users.size()); // index already updated
        users = JOhm.find(User.class, "age", 66);
        assertEquals(1, users.size());

        JOhm.delete(User.class, id);

        users = JOhm.find(User.class, "age", 88);
        assertEquals(0, users.size());
        users = JOhm.find(User.class, "age", 77);
        assertEquals(0, users.size());
        users = JOhm.find(User.class, "age", 66);
        assertEquals(0, users.size());

        assertNull(JOhm.get(User.class, id));
    } 
                            #location 13 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void cannotSearchAfterDeletingIndexes() {
        User user = new User();
        user.setAge(88);
        JOhm.save(user);

        user.setAge(77); // younger
        JOhm.save(user);

        user.setAge(66); // younger still
        JOhm.save(user);

        Long id = user.getId();

        assertNotNull(JOhm.get(User.class, id));

        List<User> users = JOhm.find(User.class, "age", 88);
        assertEquals(0, users.size()); // index already updated
        users = JOhm.find(User.class, "age", 77);
        assertEquals(0, users.size()); // index already updated
        users = JOhm.find(User.class, "age", 66);
        assertEquals(1, users.size());

        JOhm.delete(User.class, id);

        users = JOhm.find(User.class, "age", 88);
        assertEquals(0, users.size());
        users = JOhm.find(User.class, "age", 77);
        assertEquals(0, users.size());
        users = JOhm.find(User.class, "age", 66);
        assertEquals(0, users.size());

        assertNull(JOhm.get(User.class, id));
    }