message: filamesh: handle empty meshes
  empty meshes would cause a OOB read.
  b/246719043
diff: @@ -369,6 +369,11 @@ int main(int argc, char* argv[]) {
  }
  }
  + if (g_mesh.parts.empty()) {
  + std::cerr << "The mesh doesn't have any parts." << std::endl;
  + return 1;
  + }
  +
  uint32_t materialCount = scene->mNumMaterials;
  for (uint32_t i = 0; i < materialCount; i++) {
  