Fix advancement logic for ensembles with accompanists
Fix advancement logic for ensembles with accompanists

If a performance has no soloist, use an ensemblist (not just any
appearance!) to determine whether the performance advances to the
next round. Some ensemble categories allow having accompanists, who
might not advance but shouldn't affect the performance itself.

richeterre/jumubase-rails,richeterre/jumubase-rails,richeterre/jumubase-rails