HPCC-8824 Remove compile warning reported from gcc

multi is a pointer, not a boolean, and has already been cleared in the clear()
call above.

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #3991 from ghalliday/issue8824

HPCC-8824 Remove compile warning reported from gcc

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>