HPCC-9764 Fix problems with lightweight join and unordered

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #4686 from ghalliday/issue9764

HPCC-9764 Fix problems with lightweight join and unordered

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>