HPCC-9782 Fix ESP core when package set not found from dali

When package set is not found from dali, getPkgSetRegistry()
returns a NULL pointer. ESP PackageProcesses service should
check the pointer before using it.

Signed-off-by: Kevin Wang <kevin.wang@lexisnexis.com>
Merge pull request #4685 from wangkx/h9782

HPCC-9782 Fix ESP core when package set not found from dali

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>