There's no danger of ice crystals
forming in the emulsion due to freezing, the water content of dry gelatin is too small. If you want chapter & verse on pretty much everything traditional permanence related, inc freezing, download the Wilhelm book;
http://www.wilhelm-research.com/book_toc.html
This used to be a £75 hardback, but Wilhelm didn't republish when they focussed their attention on d*gital permanence, hence it was placed online.