Fix crash exporting org audit

[mbarton]

and add some logging so we can go and look and see which field is wrong.

Crash logs:

Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/django/core/handlers/exception.py", line 55, in inner
    response = get_response(request)
               ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/core/handlers/base.py", line 197, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/contrib/admin/options.py", line 718, in wrapper
    return self.admin_site.admin_view(view)(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/utils/decorators.py", line 188, in _view_wrapper
    result = _process_exception(request, e)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/utils/decorators.py", line 186, in _view_wrapper
    response = view_func(request, *args, **kwargs)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/views/decorators/cache.py", line 80, in _view_wrapper
    response = view_func(request, *args, **kwargs)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/contrib/admin/sites.py", line 241, in inner
    return view(request, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/utils/decorators.py", line 48, in _wrapper
    return bound_method(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/utils/decorators.py", line 188, in _view_wrapper
    result = _process_exception(request, e)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/utils/decorators.py", line 186, in _view_wrapper
    response = view_func(request, *args, **kwargs)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/contrib/admin/options.py", line 2034, in changelist_view
    response = self.response_action(
              
  File "/usr/local/lib/python3.11/site-packages/django/contrib/admin/options.py", line 1666, in response_action
    response = func(self, request, queryset)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/epilepsy12/admin.py", line 153, in download
    data = export_submission_period_as_csv(submission_period)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/epilepsy12/organisational_audit.py", line 160, in export_submission_period_as_csv
    selected_choices = list(value)
                       ^^^^^^^^^^^

Exception Type: TypeError at /admin/epilepsy12/organisationalauditsubmissionperiod/
Exception Value: 'NoneType' object is not iterable

[mbarton]

Overdue on STAGING, LIVE (merged by @mbarton 30 minutes and 4 seconds ago) What's gone wrong?

[mbarton]

Seen on STAGING (merged by @mbarton 31 minutes and 8 seconds ago) Please check your changes!

[mbarton]

Seen on LIVE (merged by @mbarton 31 minutes and 13 seconds ago) Please check your changes!

[mbarton]

The crash happened because we had seeded data from that trust from the previous year but they had not submitted any new data, so the new questions were None.