Loader fails when USDZ contains animations

[LucaFilitz]

When you load a USDZ file that contains animations, the loader fails to load any meshes (array is empty).

You can verify that by loading these files in the demo from the readme:

• https://developer.apple.com/augmented-reality/quick-look/models/stratocaster/fender_stratocaster.usdz (still, working)
• https://developer.apple.com/augmented-reality/quick-look/models/drummertoy/toy_drummer_idle.usdz (animated, not working)

Since the readme explicitly states that animtions are supported this is very weird behavior.

[LucaFilitz]

I pretty much get the same errors like described here: #6