FIX: allow editing in composer before a category is selected (PR #10724)

If the site setting allow_uncategorized_topics is disabled, but no site categories have a topic template, the textarea of the composer should be enabled. This allows for a post body to be entered, however the post/topic should not be successfully created until a category is selected.

If allow_uncategorized_topics is disabled and one or more categories have a topic template, the textarea of the composer should remain disabled until a category is chosen (so that the body of their post isn’t overwritten by the template).

GitHub

I don’t think we should run this check every single time the property is computed (looks like whenever the current category is changed). Can you memoize it in the model?