HPCC-9893 Fix core caused by invalid inline dataset syntax

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #4781 from ghalliday/issue9893

HPCC-9893 Fix core caused by invalid inline dataset syntax 

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>