Why am I getting an 'Affiliations Required' error when trying to delete or edit an offline gift?

This is a strange edge case that can come up when affiliations are required on the campaign.

To fix:

1. Go to form builder for the form that has affiliations (usually the prepayment, but sometimes post payment) and disable 'required' for affiliations.

2. Go to form builder for the match/challenge form and disable 'required' for affiliations.

3. Make the necessary changes to offline gifts

4. Reenable 'required' for affiliations on all forms.