#vulnerable code 
                                private boolean internalAdd(T element) {
        boolean success = nest.cat(JOhmUtils.getId(owner)).cat(field.getName())
                .rpush(JOhmUtils.getId(element).toString()) > 0;
        indexValue(element);
        return success;
    } 
                            #location 3 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                private boolean internalAdd(T element) {
        boolean success = false;
        if (element != null) {
            success = nest.cat(JOhmUtils.getId(owner)).cat(field.getName())
                    .rpush(JOhmUtils.getId(element).toString()) > 0;
            indexValue(element);
        }
        return success;
    }