Fix #124009: Clamp material index when uploading mesh through Hydra

Prevent crash from a mesh created around the time of Blender 4.0 with
bad (negative) material indices on some faces.

The Poly Haven folks were poked to fix the actual asset as well but it's
simple enough for us to clamp in this code path, especially since we
were already doing it for the upper bound.

Pull Request: https://projects.blender.org/blender/blender/pulls/124026

source/blender/io/usd/hydra/mesh.cc

@@ -400,7 +400,7 @@ void MeshData::write_submeshes(const Mesh *mesh)
   IndexMask::from_groups<int>(
       corner_tris.index_range(),
       memory,
-      [&](const int i) { return std::min(material_indices[tri_faces[i]], max_index); },
+      [&](const int i) { return std::clamp(material_indices[tri_faces[i]], 0, max_index); },
       triangles_by_material);
 
   threading::parallel_for(submeshes_.index_range(), 1, [&](const IndexRange range) {