scene: Improve behavior when failing to load a file

[mwestphal]

TODO:

• Open an issue to improve behavior: When using multi-file-mode with an invalid file, no file is loaded, but we could load some files instead #1885

[github-actions]

You are modifying libf3d public API! ⚠️Please update bindings accordingly⚠️!
You can find them in their respective directories: python, java, webassembly.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.67%. Comparing base (f7c4796) to head (b5792d4).
Report is 464 commits behind head on release.

Additional details and impacted files

@@             Coverage Diff             @@
##           release    #1883      +/-   ##
===========================================
- Coverage    96.41%   95.67%   -0.75%     
===========================================
  Files          131      125       -6     
  Lines         8042     9937    +1895     
===========================================
+ Hits          7754     9507    +1753     
- Misses         288      430     +142     

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