HPCC-9525 Segmentation fault when remote copy

This was a regression introduced since candidate-4.0.0 rc9, and not in any
released build.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #4522 from richardkchapman/issue9525

HPCC-9525 Segmentation fault when remote copy

Reviewed-By: Jake Smith <jake.smith@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>