message: add another test for unnesting NULL values
diff: @@ -27,6 +27,11 @@ a
  a
  a
  +query T
  +SELECT UNNEST(string_split(NULL, ' ')) IS NULL LIMIT 5
  +----
  +1
  +
  # now continue with string split testing
  query I
  SELECT UNNEST(string_split(string_agg(range, 'DUCK '), ' ')) AS s, mod(range, 100) xx FROM range(50000) GROUP BY xx ORDER BY s
  