Does a potion of healing hurt undead?

The other night one of my players thought it a good idea to throw a potion of healing at the undead skeletal mage. Her idea was that the potion would harm undead. A creative idea and I said go ahead, but I really didn’t know what to do.

Luckily she rolled a one and the potion smashed against the wall behind the skeletal mage. I had the mage take one of his bony fingers, scrape some of the potion off the wall, and apply it to his mouth saying he was healed 1 hp point.

My thoughts were healing potions are not radiant, therefore it would not hurt him. Was I wrong in my jugement?

Thanks 🙂