Mixedrealitytoolkit-unity: Assertion failed on expression: '!name.empty()' on import of the Examples package

[elbuhofantasma]

Describe the bug

When importing the Examples '.unitypackage', the Error "Assertion failed on expression: '!name.empty()'" was output in the Unity console. The Unity console does not display any other information about this Error.

To reproduce

Steps to reproduce the behavior:

1. Create a new Unity 2019.4.9f1 project for the Standalone platform.
2. Import the 2.5-20200901.2 Foundation package and deselect the Legacy XR option in the MRTK configuration prompt, then click apply.
3. Import the 2.5-20200901.2 Examples package and deselect the Legacy XR option in the MRTK configuration prompt, then click apply.
4. Check the Unity console output for this error.

Expected behavior

The Unity console should display more helpful information to the user when issues generated by the MRTK occur. There should also be no Errors when importing the '.unitypackage' for MRTK Examples.

Screenshots

Your setup (please complete the following information)

• Unity Version 2019.4.9f1
• MRTK Version 2.5-20200901.2

Target platform (please complete the following information)

• Standalone

Additional context

Unity log output:
``` Start importing Assets/MRTK/Examples/Demos/Gltf/Models/Cube/GLB/cube-with-custom-attr.glb using Guid(f0bb9fb635c69be4e8526b0fb6b48f39) Importer(-1,00000000000000000000000000000000)
Assertion failed on expression: '!name.empty()'
(Filename: C:\buildslave\unity\build\Editor/Src/AssetPipeline/AssetImporter.cpp Line: 401)

Done importing asset: 'Assets/MRTK/Examples/Demos/Gltf/Models/Cube/GLB/cube-with-custom-attr.glb' (target hash: 'd57eac617bb032d3e4d36697a6021407') in 0.286782 seconds ```

[wiwei]

I think we've seen this issue pop up in the past - it's a bit tricky because of the fact that the assertion is happening in Unity asset importing code.

We've also hit some other challenges associated with the GLTF loading code (right now we're still on a fork that has basically has diverged from the source quite a bit), so there might be a more holistic solution here involving doing the GLTF work correctly (i.e. as some non-forked approach, since it's caused issues around duplicate loaders and other things in the past)

[elbuhofantasma]

This issue also occurs on this commit: https://github.com/microsoft/MixedRealityToolkit-Unity/commit/a97278881a9a72d24326609fa40c963bce530442