Bug when Mixed Gravedigger spawned by Tomb Raiser Zombie

There is a bug where when Tomb Raiser attacks the Plant Hero and summons a gravestone that is Mixed Gravedigger. It's weird because Mixed Gravedigger has no gravestone ability. 

When this happens, the match will be stuck like this forever. Until one of us concedes. 

 There are more glitches like this in the link.

http://plantsvszombies.wikia.com/wiki/Plants_vs._Zombies_Heroes/Glitches