HPCC-9660 Fix optimization of a DENORMALIZE with an empty rhs

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #4616 from ghalliday/issue9660

HPCC-9660 Fix optimization of a DENORMALIZE with an empty rhs

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>
Merge remote-tracking branch 'origin/candidate-4.0.0' into closedown-4.0.x

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>