jjui doesn't handle empty revsets well. Two ways to repro:

1. jjui -r 'none()'
   • expected behavior: empty list
   • actual behavior: it shows "loading" forever
2. jjui, then hit 'L' and change the revset to none()
   • expected behavior: empty list
   • actual behavior: the old list remains on screen

Maybe instead of a blank screen, it could show "(no matching revisions)" or similar