Bug with undoing Propaganda payment

Probably somehow related to my PR #4950 - if you're paying for an effect like Propaganda or Ghostly Prison and you pay for it with a mana source with a cost such as a Signet (it might or might not happen on regular costless mana sources, I need to test more), removing the attacker from the assignment doesn't give you back your mana. I believe the game bookmarks are getting mixed up during the process and the game undoes to an incorrect one.