This should be no issue. On his iPad, just delete the app and
then reinstall it. Since there's no data in it, he won't lose
anything. Just make sure to tell him that whatever Master Password
he does choose, we can not help him unlock that file if he forgets
it again, so he needs to not only pick something he'll remember,
but add a good hint as well so he can remember. That hint is the
ONLY way he can get back into his file.
If he has the corresponding 1Password app for his Mac or Windows
machine, he might want to consider syncing his data via Dropbox.
That way he always has his data.