Cannot edit form with an empty ID field

[vinayvenu]

Describe the bug
Consider an enrolment form that has an empty ID field. If the enrolment form is being edited, then the application fails with the following error.

Fatal error: Error: Cannot modify managed objects outside of a write transaction.

To Reproduce
Steps to reproduce the behavior:

1. Manually modify an enrolment, and remove the id field from an existing enrolment.
2. Sync and edit the enrolment form

Expected behavior
This is usually not an expected flow. However, these flows can come about when a new ID field is introduced and an old form is being modified.