On wide screens, pagination is shown above and below the content (in this specific case: the threads on that forum page).
If there is only one thread and the author of this thread is ignored (which is the case according to your bug description) no thread is displayed at all - but the pagination is still displayed.
On narrow screens, pagination is only shown below the content.
Personally I'd consider this somewaht working as designed.
Actually, if the page starts on an ignored post, I guess we could say that the page shouldn't be displayed at all. But I don't think that logic is built into XF. Plus, it takes away the ability to "show ignored content" if the visitor desires.