Fix error on issues list due to restricted visibility level

What does this MR do and why?

When the public level is restricted, the issues list throws an error when signed out because it queries GraphQL for users which responds with an error since public level restriction disallows that. This MR fixes this error.

Screenshots or screen recordings

before	after

How to set up and validate locally

1. In admin settings (http://127.0.0.1:3000/admin/application_settings/general), expand Visibility and access controls and check Public within the Restricted visibility levels section
2. Visit an issues list page while signed out and confirm there's no error and the issues list shows no users, e.g. http://127.0.0.1:3000/h5bp/html5-boilerplate/-/issues/

MR acceptance checklist

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