white chocolate isn't even actually chocolate (as far as I know, there's no cocoa used to make it) so don't worry
. And as far as real chocolate goes, they really do have to eat a LOT of it to have a problem, and it's usually just diarhea. It's not "poison" to them, just bad for them and can be toxic if large quantities are eaten.
My sister in law's lab mix ate 4 entire chocolate bars once
and he was completely fine except for some loose stool for 2 days.
Relax, you're fine