Only Post field values are saved if there are Post fields

[zackkatz]

If there are Post fields in Edit Entry configuration, then non-Post fields aren't saved during Edit Entry.

✅ All Post fields: Works as expected
✅ All non-Post fields: Works as expected
✅ Form has Post fields, but not included in Edit Entry configuration

To reproduce:

1. Create a form
2. Add non-Post fields
3. Edit an entry. It works.
4. Add a Post field
5. Edit the entry. Post values are updated, but non-Post field values are not.

┆Issue is synchronized with this Asana task

[rafaehlers]

Related: https://secure.helpscout.net/conversation/251705514/6923/