django.urls.exceptions.NoReverseMatch error when opening empty content list

[timobrembeck]

Describe the Bug

When the page/event/location/imprint/push notification lists are opened in a region without a language tree, an error occurs.

Steps to Reproduce

1. Create empty region
2. Go to e.g. page tree
3. See error

Expected Behavior

One should be redirected to the language tree to create nodes

Actual Behavior

django.urls.exceptions.NoReverseMatch: Reverse for 'language_tree' not found. 'language_tree' is not a valid view function or pattern name.

Additional Information

Traceback

Internal Server Error: /empty/pages/
Traceback (most recent call last):
File "/home/timo/job/integreat/integreat-cms/.venv/lib/python3.10/site-packages/django/core/handlers/exception.py", line 47, in inner
  response = get_response(request)
File "/home/timo/job/integreat/integreat-cms/.venv/lib/python3.10/site-packages/django/core/handlers/base.py", line 181, in _get_response
  response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/home/timo/job/integreat/integreat-cms/.venv/lib/python3.10/site-packages/django/views/generic/base.py", line 70, in view
  return self.dispatch(request, *args, **kwargs)
File "/home/timo/job/integreat/integreat-cms/.venv/lib/python3.10/site-packages/django/utils/decorators.py", line 43, in _wrapper
  return bound_method(*args, **kwargs)
File "/home/timo/job/integreat/integreat-cms/.venv/lib/python3.10/site-packages/django/contrib/auth/decorators.py", line 21, in _wrapped_view
  return view_func(request, *args, **kwargs)
File "/home/timo/job/integreat/integreat-cms/.venv/lib/python3.10/site-packages/django/views/generic/base.py", line 98, in dispatch
  return handler(request, *args, **kwargs)
File "/home/timo/job/integreat/integreat-cms/integreat_cms/cms/views/pages/page_tree_view.py", line 83, in get
  return redirect(
File "/home/timo/job/integreat/integreat-cms/.venv/lib/python3.10/site-packages/django/shortcuts.py", line 41, in redirect
  return redirect_class(resolve_url(to, *args, **kwargs))
File "/home/timo/job/integreat/integreat-cms/.venv/lib/python3.10/site-packages/django/shortcuts.py", line 130, in resolve_url
  return reverse(to, args=args, kwargs=kwargs)
File "/home/timo/job/integreat/integreat-cms/.venv/lib/python3.10/site-packages/django/urls/base.py", line 86, in reverse
  return resolver._reverse_with_prefix(view, prefix, *args, **kwargs)
File "/home/timo/job/integreat/integreat-cms/.venv/lib/python3.10/site-packages/django/urls/resolvers.py", line 698, in _reverse_with_prefix
  raise NoReverseMatch(msg)
django.urls.exceptions.NoReverseMatch: Reverse for 'language_tree' not found. 'language_tree' is not a valid view function or pattern name.

This is a regression from b2eaf7e.