HPCC-10684 - Prevent close of old + start of new session clashing

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #5294 from jakesmith/hpcc-10684

HPCC-10684 - Prevent close of old + start of new session clashing

Reviewed-By: Gavin Halliday <gavin.halliday@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>