Reimporting assets that use KHR_materials_variants breaks variants

[The0Dev]

Describe the bug
When I export an asset that uses KHR_materials_variants and import it back it somehow ends up broken.

To Reproduce
Steps to reproduce the behavior:

1. Import suzanne_mv_test.glb (this asset passes validation without any errors and can be viewed in Babylon.js)
2. See that variants are not displayed properly.
   Exporting this asset back produces a broken gltf file.
   

Expected behavior
It should be possible to export and reimport assets that use KHR_materials_variants and preserve their functionality.

.blend file/ .gltf (mandatory)
material_variants.zip

Version

• OS: Linux
• Blender Version: 4.2

[julienduroure]

Confirmed.
The root issue is not the import, neither re-exporting it.
But the root cause is the initial export that creates the suzanne_mv_test.glb file, with extras.
This extras (that store variant) info needs to be excluded from export.
Because, when importing variants + extras, there are some conflict.

Tested with importing without any extras (in debug), and can see the variants, and re-export is OK (tested in babylonjs)