HPCC-10184 Potential memory leak in uncompress routine

In the event of an exception in the expander, the memory buffer being
expanded into is not freed.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #4966 from richardkchapman/uncompress-leak-on-exception

HPCC-10184 Potential memory leak in uncompress routine

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>