TypeError: '<' not supported between instances of 'NoneType' and 'NoneType'

[JonBendtsen]

I was editing an event with 3 teachers, 2 teachers has 4 hours each, 3. teacher has 8 hours.

Date was specified, but NOT time because I do not yet know when on the day it starts

Internal Server Error: /admin/core/event/add/
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.10/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.10/site-packages/django/contrib/admin/options.py", line 614, in wrapper
    return self.admin_site.admin_view(view)(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/django/utils/decorators.py", line 130, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/django/views/decorators/cache.py", line 44, in _wrapped_view_func
    response = view_func(request, *args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/django/contrib/admin/sites.py", line 233, in inner
    return view(request, *args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/polymorphic/admin/parentadmin.py", line 211, in add_view
    return real_admin.add_view(request, form_url, extra_context)
  File "/usr/local/lib/python3.10/site-packages/django/contrib/admin/options.py", line 1653, in add_view
    return self.changeform_view(request, None, form_url, extra_context)
  File "/usr/local/lib/python3.10/site-packages/django/utils/decorators.py", line 43, in _wrapper
    return bound_method(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/django/utils/decorators.py", line 130, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/django/contrib/admin/options.py", line 1534, in changeform_view
    return self._changeform_view(request, object_id, form_url, extra_context)
  File "/usr/local/lib/python3.10/site-packages/django/contrib/admin/options.py", line 1579, in _changeform_view
    if all_valid(formsets) and form_validated:
  File "/usr/local/lib/python3.10/site-packages/django/forms/formsets.py", line 464, in all_valid
    valid &= formset.is_valid()
  File "/usr/local/lib/python3.10/site-packages/django/forms/formsets.py", line 308, in is_valid
    self.errors
  File "/usr/local/lib/python3.10/site-packages/django/forms/formsets.py", line 288, in errors
    self.full_clean()
  File "/usr/local/lib/python3.10/site-packages/django/forms/formsets.py", line 336, in full_clean
    form_errors = form.errors
  File "/usr/local/lib/python3.10/site-packages/django/forms/forms.py", line 172, in errors
    self.full_clean()
  File "/usr/local/lib/python3.10/site-packages/django/forms/forms.py", line 376, in full_clean
    self._post_clean()
  File "/usr/local/lib/python3.10/site-packages/django/forms/models.py", line 405, in _post_clean
    self.instance.full_clean(exclude=exclude, validate_unique=False)
  File "/usr/local/lib/python3.10/site-packages/django/db/models/base.py", line 1216, in full_clean
    self.clean()
  File "/usr/local/lib/python3.10/site-packages/danceschool/core/models.py", line 1625, in clean
    if self.endTime < self.startTime:
TypeError: '<' not supported between instances of 'NoneType' and 'NoneType'

[JonBendtsen]

yeah, removing the Event occurrences "lines" with dates and I could save just fine this time.