I think I have detected a small bug. I will detail it.
I created a club. Call it "New club"
I created a forum in the club. Call it "New Forum"
I added content ( maybe this is not related but I added 2 topics )
Moved the 2 topics to another forum, (not in the clubs)
I deleted the forum "New Forum"
But, the "New Forum" still appears in the list, not only for the group leader, but also for members.
You can click on the link and it redirects to the club main section, since the forum no longer exists.
I tried to clear cache using the support tool, just in case it was something stuck there, but the issue still there.
The bottom line is that when you delete a forum in a club, it does not disappear.
Using version 4.4.3