Invulnerable practice tool towers can be damaged by demolish

I was messing with GP in practice tool. had an ai that was rammus while i was fast forwarding to get minions to q i noticed mid was damaged which was weird since i had towers set to invulnerable. i heard demolish sounds so i waited and watched rammus and when it came off cd he did it again and i noticed it was damaging towers while nothing else was

This probably isn't a big deal since it's a minor thing in practice tool, but it seems like a bug and i guess if there's ever some really whacky thing in the real game that makes towers invuln temporarily make sure you fix this for that.