Add coco manual validation for the cases which are not possible to cover

There are certain validations that are reasonable to do, but the exception is in real life catched earlier phase on the execution path. Add coco validated block to the cases which are not possible to reach in unit tests:

http://ci-files02-hki.intra.qt.io/packages/jenkins/qtsaferenderer/nightly/html/1.2/2021-02-20.00.01.01/QSR_nightly_Linux_Autotest_Multiple_Condition_Code_Coverage_200221_html/source_6.html#line110