HPCC-7950 Fix minor compile error introduced by previous change

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #3846 from ghalliday/issue7950b

HPCC-7950 Fix minor compile error introduced by previous change

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>