ROLLUP query returns incorrect result with empty result set

Similar to MySQL Bug #36514339, documented in 9.1.0 changelog: https://dev.mysql.com/doc/relnotes/mysql/9.7/en/news-9-1-0.html

When running a ROLLUP query on an empty table, e.g.

CREATE TABLE t0(x INT);

SELECT * FROM t0 GROUP BY x WITH ROLLUP;

We should get a single grouping row with null entries for all fields in GROUP BY (i.e. the grand total row produced by ROLLUP). However, MariaDB returns an empty set instead.