Return first geometryBuffer if no best match found

[ljowen]

Description

If no exact match by attribute is found in _findBestGeometryBuffers return the first one. I believe this was the original intention with this function returning 0 for the index.

This allows I3S Scenes to render with geometries missing either ["position", "uv0"] (See issue / sandcastle).

Issue number and link

Fixes #12114

Testing plan

• Create sandcastle with the following added as an I3S dataProvider:
  • https://basemaps3d.arcgis.com/arcgis/rest/services/OpenStreetMap3D_Buildings_v1/SceneServer?layers=ca0470dbbddb4db28bad74ed39949e25
• Verify the scene renders and errors are no longer thrown
• Confirm other I3S scenes are rendering fine

Sandcastle Link

Author checklist

• I have submitted a Contributor License Agreement
• I have added my name to CONTRIBUTORS.md
• I have updated CHANGES.md with a short summary of my change
• I have added or updated unit tests to ensure consistent code coverage
• I have updated the inline documentation, and included code examples where relevant
• I have performed a self-review of my code

[github-actions]

Thank you for the pull request, @ljowen!

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