500 when ansible-client acceses distribution that does not point to repository

[ipanova]

Version
pulp-ansible 0.14

Describe the bug
A clear and concise description of what the bug is.

To Reproduce

$ pulp ansible distribution create --name "test" --base-path "test"
Started background task /pulp/api/v3/tasks/6cc0bcd8-e767-47ec-85a4-fc229ba72c6c/
Done.
{
  "pulp_href": "/pulp/api/v3/distributions/ansible/ansible/66fbcc7d-4f9a-4dcd-ac0d-f917b1d70716/",
  "pulp_created": "2022-04-12T09:43:01.329738Z",
  "base_path": "test",
  "content_guard": null,
  "name": "test",
  "repository": null,
  "repository_version": null,
  "client_url": "https://pulp3-source-fedora34.fluffy.example.com/pulp_ansible/galaxy/test/",
  "pulp_labels": {}
}

(pulp) [vagrant@pulp3-source-fedora34 pulpcore]$ ansible-galaxy install -vv elasticsearch,6.2.4 -c -s https://pulp3-source-fedora34.fluffy.example.com/pulp_ansible/galaxy/test/
ansible-galaxy [core 2.12.4]
  config file = None
  configured module search path = ['/home/vagrant/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/pulp/lib64/python3.9/site-packages/ansible
  ansible collection location = /home/vagrant/.ansible/collections:/usr/share/ansible/collections
  executable location = /usr/local/lib/pulp/bin/ansible-galaxy
  python version = 3.9.7 (default, Aug 30 2021, 00:00:00) [GCC 11.2.1 20210728 (Red Hat 11.2.1-1)]
  jinja version = 3.0.1
  libyaml = True
No config file found; using defaults
Starting galaxy role install process
- downloading role 'elasticsearch', owned by 
[WARNING]: - elasticsearch was NOT installed successfully: None (HTTP Code: 500, Message: Internal Server Error)
ERROR! - you can use --ignore-errors to skip failed roles and finish processing the list.

Traceback form the logs:

pulp [e4a12db90fe04f448772c444301dbb21]:  - admin [12/Apr/2022:09:43:11 +0000] "GET /pulp_ansible/galaxy/test/api/v1/roles/?owner__username=&name=elasticsearch HT>
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]: AttributeError: 'NoneType' object has no attribute 'latest_version'
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:     distro_content = distro.repository.latest_version().content
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:   File "/home/vagrant/devel/pulp_ansible/pulp_ansible/app/galaxy/views.py", line 68, in get_queryset
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:     queryset = self.filter_queryset(self.get_queryset())
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:   File "/usr/local/lib/pulp/lib64/python3.9/site-packages/rest_framework/mixins.py", line 38, in list
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:     return self.list(request, *args, **kwargs)
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:   File "/usr/local/lib/pulp/lib64/python3.9/site-packages/rest_framework/generics.py", line 199, in get
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:     response = handler(request, *args, **kwargs)
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:   File "/usr/local/lib/pulp/lib64/python3.9/site-packages/rest_framework/views.py", line 506, in dispatch
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:     raise exc
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:   File "/usr/local/lib/pulp/lib64/python3.9/site-packages/rest_framework/views.py", line 480, in raise_uncaught_exception
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:     self.raise_uncaught_exception(exc)
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:   File "/usr/local/lib/pulp/lib64/python3.9/site-packages/rest_framework/views.py", line 469, in handle_exception
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:     response = self.handle_exception(exc)
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:   File "/usr/local/lib/pulp/lib64/python3.9/site-packages/rest_framework/views.py", line 509, in dispatch
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:     return self.dispatch(request, *args, **kwargs)
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:   File "/usr/local/lib/pulp/lib64/python3.9/site-packages/django/views/generic/base.py", line 70, in view
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:     return view_func(*args, **kwargs)
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:   File "/usr/local/lib/pulp/lib64/python3.9/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:     response = wrapped_callback(request, *callback_args, **callback_kwargs)
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:   File "/usr/local/lib/pulp/lib64/python3.9/site-packages/django/core/handlers/base.py", line 181, in _get_response
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:     response = get_response(request)
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]:   File "/usr/local/lib/pulp/lib64/python3.9/site-packages/django/core/handlers/exception.py", line 47, in inner
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]: Traceback (most recent call last):
Apr 12 09:43:11 pulp3-source-fedora34.fluffy.example.com gunicorn[100411]: pulp [e4a12db90fe04f448772c444301dbb21]: django.request:ERROR: Internal Server Error: /pulp_ansible/galaxy/test/api/v1/roles/

Expected behavior
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Additional context
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