Issue: Hide Empty Category Lists from Guests/Google (SEO issue)

There is not adequate information available to know whether the list will be empty before navigating onto it, so it would not be possible to completely hide the links from guests only when empty, without adding a few potentially expensive queries to the page that has the link for the single purpose of testing the link.

The links to those lists are nofollow, so Google will not crawl onto them.

The lists could do with adding noindex to them if they are empty, in case Google gets to them a different way (such as a user-generated link). At this point, this would be the only change I feel comfortable with.

That sounds like a good idea to me.