#vulnerable code 
                                @Test
    public void testUpdate() {
        redisSessionDAO.doCreate(session1);
        doChangeSessionName(session1, name1);
        redisSessionDAO.update(session1);
        FakeSession actualSession = (FakeSession)redisSessionDAO.doReadSession(session1.getId());
        assertEquals(actualSession.getName(), name1);
    } 
                            #location 7 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testUpdate() {
        redisSessionDAO.doCreate(session1);
        redisSessionDAO.doReadSession(session1.getId());
        doChangeSessionName(session1, name1);
        redisSessionDAO.update(session1);
        FakeSession actualSession = (FakeSession)redisSessionDAO.doReadSession(session1.getId());
        assertEquals(actualSession.getName(), name1);
    }