Koha allows for ILL requests without patrons, and since bug 32630 this may happen more often. Backends compatible with ILLOpacUnauthenticatedRequest will likely have requests without patrons associated, but may still need to make use of Koha::ILL::Request::get_notice (e.g. Koha2Koha backend https://gitlab.com/koha-community/plugins/koha-plugin-ill-koha) get_notice should be more defensive and consider the possibility of the request not having a patron. Core Koha should handle this validation, the alternative is every backend in this scenario needs to handle it.
This is actually handled by bug 32630 already. Missed it while working on a 24.11.x branch.