Unchecked boolean CPF state is lost when form submission is rejected

Found this while testing http://tracker.phpbb.com/browse/PHPBB3-10599?focusedCommentId=37431#comment-37431.

I created two boolean CPFs, one required and one not required. I registered checking both. Then I went to ucp profile page and unchecked both and attempted to submit the form.

The submission was rejected because the required boolean CPF must have been checked. However the not required CPF was reset back to checked. It should have been unchecked since that was a valid operation.

On registration form this did not happen.