The bug in #4438 happened because of an unset serial number, and a fix is in progress in #4440

What I'd like is some improved tests for unset data in output_engine so this doesn't happen again, so I want a test that tries to run output_engine/__init__.py with various values not set.

I have a feeling that any test that cycles through all the possible fields will right now find a few bugs, so we may want to start with just sbom_serial_number but design it so that we can have a parameter test with any given field unset so eventually all possible fields will be tested.