Also an invalid clause. They don't get to decide what is valid or not, that's up to the judge.
I am not a lawyer, this isn't legal advice.
It's up to the judge to decide what is valid and not. The court has the power to decide on each clause individually and the contract as a whole.
It's the normal outcome that when one minor clause is deemed invalid, only that clause is dismissed, not the whole contract.
It doesn't costs anything to write it down to clarify. That's exactly why it's written in every standard contract. There could be a different jurisdiction somewhere one day that decides to invalidate entire contracts by default for any stupid reason, I don't know of one in the western countries but I suppose it's possible.