You might be misunderstanding the question. Conflict doesn't necessarily mean "having a row", actually it should never mean that, especially at work.

It's hard to believe you've never:

- had a different opinion on the priorities/ course of action/ risks involved in something or anything else than your boss
- disagreed on how to tackle something with your colleague
- wanted something your boss didn't want to provide you
- disagreed with any element of the company's strategy/ decision

These situations are so omnipresent that saying "I've never had any conflict" just means you don't notice them. Or you are a yea-sayer, not able to voice a different opinion, which can be problematic if the company expects its employees to be innovative or signal risks for example.

No one expects the answer to this question to be super creative. It's a question about how you deal with what is a normal, daily situation. Searching for the best solution together is normally considered good as is convincing someone. Withdrawing or agression isn't.