Bug: Dashboard extra gradings doesn't accept final skip

[enbyboiwonder]

@NihongoLearner19 has had it happen too; they mentioned it in the casual discussion thread:

@NihongoLearner19

I’ve had that happen too, where I try to skip a grading and it doesn’t work. If I come back to grade again later, the same comparison comes up. I think it’s a bug.