AttributeError when trying to create transcriptions on an element without a zone

Sentry Issue: ARKINDEX-BACKEND-40

AttributeError: 'NoneType' object has no attribute 'image'
(7 additional frame(s) were not displayed)
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  File "rest_framework/views.py", line 502, in dispatch
    response = handler(request, *args, **kwargs)
  File "rest_framework/generics.py", line 190, in post
    return self.create(request, *args, **kwargs)
  File "arkindex/documents/api/ml.py", line 178, in create
    annotations = self.perform_create(serializer)
  File "contextlib.py", line 74, in inner
    return func(*args, **kwds)
  File "arkindex/documents/api/ml.py", line 197, in perform_create
    image = self.element.zone.image