I know this may be bit of pain to do but possibly this can be included in a future version.
Within Groups, Spaces etc, one has the ability to add a Popular Hashtags and [GROUP or SPACE] Categories block to the [GROUP or SPACE] in context page [GROUP or SPACE] of author page, the Popular Hashtags block and Categories block include all Hashtags and Categories.
It would be useful to limit these to only categories and hashtags that exist with the context of that Group or Space, not include hashtags that may have no bearing on any published content within that [GROUP or SPACE].
At the moment a user can click on a category within a [GROUP or SPACE] that indicates that there are X number of posts/videos etc available and when they click on the category no results are returned as those pieces of content do not exist within the current Context.
Even if the category remain but the content counter is updated that would also suffice. As for Hashtags, I know this can be challenging due to the overhead this may cause on that page, so if I had a vote, Categories takes precedence.
This can and has caused some frustration amongst many of our users.