runner: Avoid a possible NullPointerException with tCase Object

Change-Id: Ie1202b7fa89306ea2a99031b9347b657039b839e
Reviewed-on: https://gerrit.libreoffice.org/11750
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>