Fixting Stitching Bug

[captain-pool]

Hi Mike,
Thanks again for sharing trimesh with the community. I noticed a tiny bug in the implementation of "stitch()". More specifically: the implementation of unitize(...)

trimesh/trimesh/util.py

Lines 128 to 129 in aa3cb56

	if check_valid:
	return unit[valid], valid

returns the normals after masking with valid when check_valid=True. However, in the current implementation of stitch

trimesh/trimesh/repair.py

Line 438 in 3d5af39

check = check[valid][0]

the mask is applied again on the masked results, causing it the function to break.

This PR contains a quick fix to the problem.

Thanks.
-- Adrish

[mikedh]

Good catch, thanks for the fix!