I'm not exactly sure on the reproduction scenario here, but I have had
switching ruleset with converts disabled crash on me a few times
today. It appears to happen sometimes when after the switch the expanded
group no longer exists in the set mapping, because a filter just ran and
removed that group from set of possible groups because there'd be no
beatmaps under it.
I tried to manufacture a quick test but it's not a quick one to test
because filtering intereference is required to reproduce, I think.
I will try again on request but I mostly just want to get this fix out
ASAP before I finish up for the day.
Bartłomiej Dach
7b1e3cd537