message: gltfpack: Fix constant track handling for morph target weights
  We were mistakenly removing morph weight tracks that were constant with
  the first weight being equal to 0; for now we preserve all constant
  morph weight tracks instead.
diff: @@ -2213,6 +2213,12 @@ void markAnimated(cgltf_data* data, std::vector<NodeInfo>& nodes)
  {
  ni.animated_paths |= (1 << channel.target_path);
  }
  + else if (channel.target_path == cgltf_animation_path_type_weights)
  + {
  + // we currently preserve constant weight tracks because the usecase is very rare and
  + // isTrackConstant doesn't return the full set of weights to compare against
  + ni.animated_paths |= (1 << channel.target_path);
  + }
  else
  {
  Attr base = {};
  @@ -2228,11 +2234,10 @@ void markAnimated(cgltf_data* data, std::vector<NodeInfo>& nodes)
  case cgltf_animation_path_type_scale:
  memcpy(base.f, channel.target_node->scale, 3 * sizeof(float));
  break;
  - default:;
  + default:
  + assert(!"Unknown target path");
  }
  - // TODO: what about cgltf_animation_path_type_weights?
  -
  const float tolerance = 1e-3f;
  if (getDelta(base, first, channel.target_path) > tolerance)
  