message: demo: Fix simplify assertion for small meshes
  In some cases when target_index_count is small enough we can get a mesh
  mesh with fewer indices, and on the next iteration we can ask for more
  indices than the source mesh has, which triggers an assertion in
  meshopt_simplify.
diff: @@ -242,14 +242,14 @@ void optCompleteSimplify(Mesh& mesh)
  std::vector<unsigned int>& lod = lods[i];
  float threshold = powf(0.7f, float(i));
  - size_t target_index_count = size_t(mesh.indices.size() * threshold);
  + size_t target_index_count = size_t(mesh.indices.size() * threshold) / 3 * 3;
  // we can simplify all the way from base level or from the last result
  // simplifying from the base level sometimes produces better results, but simplifying from last level is faster
  const std::vector<unsigned int>& source = lods[i - 1];
  lod.resize(source.size());
  - lod.resize(meshopt_simplify(&lod[0], &source[0], source.size(), &mesh.vertices[0].px, mesh.vertices.size(), sizeof(Vertex), target_index_count));
  + lod.resize(meshopt_simplify(&lod[0], &source[0], source.size(), &mesh.vertices[0].px, mesh.vertices.size(), sizeof(Vertex), std::min(source.size(), target_index_count)));
  }
  // optimize each individual LOD for vertex cache & overdraw
  