[CI] Fix for create_ref_part2 in case this generates zero tests

When removing the MR pipeline test cases from the long test, the create_ref_part2 rendered zero tests. This lead to a halt in the job execution and no tests were evaluate. This fix catches the exit code such that the job execution is not halted even if zero tests are generated.

This pipeline shows the job was not fixed. Will merge this asap to fix the long tests. https://forge.3gpp.org/rep/sa4/audio/ivas-basop/-/pipelines/30698