#fixed code
                                @Test
    public void testObjectIdSaved() {
        ObjectIdId object = new ObjectIdId();
        org.bson.types.ObjectId id = new org.bson.types.ObjectId();
        object._id = id;

        JacksonDBCollection<ObjectIdId, org.bson.types.ObjectId> coll = getCollection(ObjectIdId.class,
                org.bson.types.ObjectId.class);

        coll.insert(object);
        ObjectIdId result = coll.findOneById(id);
        assertThat(result._id, equalTo(id));
        assertThat((org.bson.types.ObjectId) coll.getDbCollection().findOne().get("_id"), equalTo(id));
    }
#vulnerable code 
                                @Test
    public void testObjectIdSaved() {
        ObjectIdId object = new ObjectIdId();
        org.bson.types.ObjectId id = new org.bson.types.ObjectId();
        object._id = id;

        JacksonDBCollection<ObjectIdId, org.bson.types.ObjectId> coll = getCollection(ObjectIdId.class,
                org.bson.types.ObjectId.class);

        coll.insert(object);
        ObjectIdId result = coll.findOneById(id);
        assertThat(result._id, equalTo(id));
    } 
                            #location 12 
                            #vulnerability type NULL_DEREFERENCE