Planning error with unrelated sort columns and view removal

There is an array index out of bounds in rule merge virtual correct order by when there is an unrelated sort over a query with a grouping:

select a from (SELECT intkey as a, stringkey as b FROM BQT1.SmallA group by intkey, stringkey union all SELECT intkey as a, stringkey as b FROM BQT1.Smallb group by intkey, stringkey) as v order by b