Splash Regeneration Potion should act like poison to undead

Just like how the potion of harming heals undead but harms the living (and the potion of healing heals the living but harms the undead), the potion of regeneration should act like a splash potion of poison towards the undead (progressively harming the undead but progressively healing the living), and vice versa... A small detail, but a simple one to add. I think this will allow the game to be a little bit more coherent with the rules already in place.