fix edge case with config files pointer

[phlptp]

generating a seg fault if no default and no config file provided.

Fixes #1197

This was likely introduced by the combination of fixes for some issues with the config parsing and some updates to the as method a while back. This edge case on the handling of the config pointer with as was not overlooked in the earlier testing.

[phlptp]

this edge case could also apply if someone was manipulating and running an option callback outside of the app. The fix resolves both situations.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (e4ee3af) to head (44b50f0).
⚠️ Report is 117 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##              main     #1199     +/-   ##
===========================================
  Coverage   100.00%   100.00%             
===========================================
  Files           17        17             
  Lines         4546      5180    +634     
  Branches         0      1064   +1064     
===========================================
+ Hits          4546      5180    +634     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.