Interesting - it was deleted an hour ago, but 30 seconds after it was deleted, another user flagged it (presumably a 10k user had the flagged-posts screen open at the time). This was enough to keep it active on the 10k screen, and it subsequently attracted another 4 flags. But indeed, it has been dealt with!
Normally, the act of a moderator intervening (such as deleting the post) will wipe the flags - and indeed this did happen here; however, it was still possible for other users to flag it after it was deleted.
I will try to ensure that in the future, only custom flag reasons can be used on deleted posts; this should avoid this unnecessary scenario (i.e. the user flagging it after it was deleted would be simply told "this post has been deleted").