message: Fix MeshReader material bug
diff: @@ -373,10 +373,10 @@ MeshReader::Mesh MeshReader::loadMeshFromBuffer(filament::Engine* engine,
  partsMaterial[materialIndex].c_str(), partsMaterial[materialIndex].size());
  const auto mat = materials.getMaterialInstance(materialName);
  if (mat == nullptr) {
  - builder.material(materialIndex, defaultmi);
  + builder.material(i, defaultmi);
  materials.registerMaterialInstance(materialName, defaultmi);
  } else {
  - builder.material(materialIndex, mat);
  + builder.material(i, mat);
  }
  }
  builder.build(*engine, mesh.renderable);
  