bug: http 500 error when adding parameters with an empty value

[liske]

It seems that an empty value field is not handled when adding instances of the Parameters model:

Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/django/core/handlers/exception.py", line 38, in inner
    response = await get_response(request)
  File "/usr/local/lib/python3.10/site-packages/django/core/handlers/base.py", line 233, in _get_response_async
    response = await wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python3.10/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/usr/local/lib/python3.10/site-packages/django/contrib/admin/options.py", line 616, 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 232, in inner
    return view(request, *args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/django/contrib/admin/options.py", line 1657, 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 1540, 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
    form_validated = form.is_valid()
  File "/usr/local/lib/python3.10/site-packages/django/forms/forms.py", line 175, in is_valid
    return self.is_bound and not self.errors
  File "/usr/local/lib/python3.10/site-packages/django/forms/forms.py", line 170, in errors
    self.full_clean()
  File "/usr/local/lib/python3.10/site-packages/django/forms/forms.py", line 374, in full_clean
    self._post_clean()
  File "/usr/local/lib/python3.10/site-packages/django/forms/models.py", line 413, 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 1229, in full_clean
    self.clean_fields(exclude=exclude)
  File "/usr/src/app/rest/models.py", line 1315, in clean_fields
    if not match(self.PARAMETER_REGEXES[self.parameter], self.value):
  File "/usr/lib/python3.10/re.py", line 190, in match
    return _compile(pattern, flags).match(string)

Exception Type: TypeError at /admin/rest/parameter/add/
Exception Value: expected string or bytes-like object
Request information:
USER: XXXXXXXX

GET: No GET data

POST:
csrfmiddlewaretoken = 'XXXXXXXX'
mode = 'SET'
parameter = 'disabledFeatures'
tenant = 'XXXXXXXX'
value = ''
_save = 'Sichern'