Horse armor does not render on a horse when using resource packs with a minimum engine version of 1.17.0 or lower

Steps to reproduce:

1. Import and apply the attached resource pack: MCPE-185316.mcpack
2. Create/open a world
3. Tame a horse
4. Put any kind of horse armor on it

Observed result:
The horse armor is not rendered at all.

Expected result:
The horse armor is rendered, since the resource pack does not change its textures.