GLB loading fails with KeyError: 'POSITION'

[JulianKnodt]

Hi again,
I've found a crash where (I believe) if a node has no vertices then Trimesh fails to load a glb file.

I've had to convert it to a txt file since github doesn't support GLB files. If you'd prefer I email it to you, I can also do that.

I've verified that this occurs on Mac & Windows, with trimesh version 4.5.1.

Traceback:

File (extension is txt since I ran cp etrian_odyssey_3_monk.glb etrian_odyssey_3_monk.txt):
etrian_odyssey_3_monk.txt

As an aside, if I try to load this mesh without skip materials, it also fails, but that's avoidable by adding skip materials.