I was wondering about that my self actually xd
I think freezing the walls wpuld be more of a problem cause it might be a danger to someone in an other cell like blade
and that I dobt think that freezing walls would help
BUT Its a mechanical lock and mechincal is often not freeze proof so you might be able to break the lock
trough there is a risk that they fixed your cell but I dont see many things that can block ice out in this case
electronics also break with ice xd