Category dropdown missing in composer

Steps to reproduce:

  1. Enable lazy-loaded-categories for a group
  2. Add a non-staff test user to that group
  3. Log in as the test user
  4. Use the Horizon theme which adds a new topic button to the sidebar or add /new-topic to a custom section in the user’s sidebar
  5. Visit the group page /g
  6. Reload
  7. Click the new topic link or button in the sidebar

Expected result: You see a composer where you can enter title, category, tags and body of your new topic.
Actual result: The category field is missing

Note: It’s not only the groups page that seems to be affected. It also happened on the profile, badges, and about page. Even from within a topic, it seems to be the same problem.