Tbf: he renewed this agreement when buying tickets which doesn't really make it better but still
Edit: since I got some downvotes and comments, I'm not saying they are in the right, all I'm relativizing is the "years earlier" at the end. The contract was renewed recently, still it totally doesn't cover this kind of situation.
Contracts can't really shield from that kind of negligence either though. You can't have someone sign a contract indemnifying you from everything and then have no culpability when you literally poison them.
I get that servers have to deal with selective gluten allergies but nut and dairy allergies are not that. They are deadly and the server/kitchen should have absolutely refused to serve any food they couldn't separate. This is basic knowledge in the food industry too, something they should have known and been trained on.