* FIX: allow editing in composer before a category is selected
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).
* Avoid recalculating hasTopicTemplates repeatedly
09a97363da