TypeError: argument of type 'NoneType' is not iterable

[sentry-io]

Sentry Issue: APPLICATION-BACKEND-8NH

TypeError: argument of type 'NoneType' is not iterable
(5 additional frame(s) were not displayed)
...
  File "api/views/emails/routes.py", line 195, in update_email
    if error := instance.validate_payload(payload.dict(exclude_unset=True)):
  File "utils/models.py", line 103, in validate_payload
    if error := check_for_validation_error(new_value):
  File "emails/models/email/model.py", line 117, in validate_body
    if "\x00" in value:

[linear]

LEG-535 TypeError: argument of type 'NoneType' is not iterable