Fix pointer error in OS_GetErrorName

[ahatstat]

Checklist (Please check before submitting)

• [x] I reviewed the Contributing Guide.
• [x] I signed and emailed the appropriate Contributor License Agreement to GSFC-SoftwareRelease@mail.nasa.gov and copied cfs-program@lists.nasa.gov.

Describe the contribution Fixes #1435

Testing performed Build and run all coverage tests including coverage-shared-errors-testrunner on ARM/Linux and PC/Ubunutu. All tests pass and do not seg fault.

Expected behavior changes Fewer seg faults when running unit tests

System(s) tested on ARM9/Embedded Linux PC/Ubuntu 22.04LTS

Additional context N/A

Third party code N/A

Contributor Info - All information REQUIRED for consideration of pull request Andrew Hatstat, Geost

[jphickey]

This looks good but I had the question of how it could have been in there for so long and never noticed. We should create a follow-on issue to investigate why this does not fail in our existing workflows