Great feature Billy, I have been looking forward to this for a while.
When I clicked on the missing episode filter before doing a missing episode scan, I got a message that there was no missing art - I'm assuming here that you copied & pasted some of the code & its duplicated that from the fanart filter.
Perhaps the message should also ask if none are found if you would like to check for missing episodes now or not. This would be especially handy for new users unfamiliar with how to find that option in the menu.
Cheers