The current implementation of ClaimManager does a bunch of checks (anonymous can't claim anything, this claim belongs to a different user, etc). This is all good and well, but users can sometimes hit those, and get an ugly exception screen. Especially in the case of "anonymous can't claim anything", they should simply be redirected to the login screen. Other cases should probably be handled more gracefully as well, but perhaps MAGNOLIA-3595 would be good enough.