Exported file is invalid because it accesess non-existing UV channels

[hybridherbst]

Two examples:
UVMismatch_UV1.glb.zip
UVMismatch_UV2.glb.zip

The files are invalid because the same material is used on multiple objects, but some of the objects don't have the specified UV channel. Theoretically, the material would need to be duplicated on export and some of the indices stripped out / adjusted to "make it work" with all models.

I'd hold off on fixing this issue until it's clear what the desired behaviour in three and glTF is (opened relevant issues there as well).