Converting GLTF vertex color to RGBA on load attempts to modify non-writable buffer

[Dan Wulczynski]

When loading GLTF(glb) containing floating point vertex color data, further down the line when visual data is assigned the call to_rgba() attempts to modify non writable color array.

trimesh/trimesh/visual/color.py

Line 583 in 7853a5e

 colors[~np.isfinite(colors)] = 0.0 

[Dan Wulczynski]

Proposed fix: #2233