Textlab widget not working for non-staff-members

[timobrembeck]

Describe the Bug

The textlab widget does not work for users who are no staff members.

Steps to Reproduce

1. Login as admin
2. Enable Textlab in a region
3. Login as non-staff in that region
4. Visit page form

Expected Behavior	Actual Behavior

Additional Information

Traceback

Nov 15 14:09:42 WARNING django.request - 403 Forbidden (Permission denied): /ajax/get_hix_score/
Traceback (most recent call last):
File "/opt/integreat-cms/.venv/lib/python3.9/site-packages/django/core/handlers/exception.py", line 47, in inner
  response = get_response(request)
File "/opt/integreat-cms/.venv/lib/python3.9/site-packages/integreat_cms/core/middleware/access_control_middleware.py", line 67, in __call__
  raise PermissionDenied(
django.core.exceptions.PermissionDenied: <SimpleLazyObject: <User (id: XXX, username: XXX, role: Manager)>> does not have the permission to access the staff area

The source of the problem is the same as in #1777.
In addition of fixing the bug, we should also improve the error handling to show an error message and hide the graph if something goes wrong.