message: gltfpack: Fix .obj texture transform export
  When creating .obj materials we weren't filling unused fields of
  cgltf_texture_transform; this resulted in .scale being set to 0.
  Fix this by only using texture info transform when has_transform is set.
diff: @@ -1400,7 +1400,16 @@ void writeTextureInfo(std::string& json, const cgltf_data* data, const cgltf_tex
  {
  assert(view.texture);
  - cgltf_texture_transform transform = view.transform;
  + cgltf_texture_transform transform = {};
  +
  + if (view.has_transform)
  + {
  + transform = view.transform;
  + }
  + else
  + {
  + transform.scale[0] = transform.scale[1] = 1.f;
  + }
  transform.offset[0] += qp.uv_offset[0];
  transform.offset[1] += qp.uv_offset[1];
  