Error when trying to archive a page without backend language translation

[seluianova]

Describe the Bug

Pages without backend language translation ( it's a CMS UI language I guess?) cannot be archived, since this action uses a title in the backend language to print a success message

Steps to Reproduce

1. Set CMS UI language to English in user settings
2. Try archiving any page without an English translation

Expected Behavior

Page can be archived

Actual Behavior

Error occurs:

Additional Information

Aug 21 20:59:47 ERROR django.request - 500 Internal Server Error: /augsburg/pages/de/bulk-archive/
Traceback (most recent call last):
  File "/home/tory/Integreat/integreat-cms/.venv/lib/python3.9/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/home/tory/Integreat/integreat-cms/.venv/lib/python3.9/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, callback_args, *callback_kwargs)
  File "/home/tory/Integreat/integreat-cms/.venv/lib/python3.9/site-packages/django/views/generic/base.py", line 70, in view
    return self.dispatch(request, args, *kwargs)
  File "/home/tory/Integreat/integreat-cms/.venv/lib/python3.9/site-packages/django/contrib/auth/mixins.py", line 104, in dispatch
    return super().dispatch(request, args, *kwargs)
  File "/home/tory/Integreat/integreat-cms/.venv/lib/python3.9/site-packages/django/views/generic/base.py", line 98, in dispatch
    return handler(request, args, *kwargs)
  File "/home/tory/Integreat/integreat-cms/integreat_cms/cms/views/bulk_action_views.py", line 288, in post
    content_object.backend_translation.title
AttributeError: 'NoneType' object has no attribute 'title'