Put the summary of the bug you're having here
What I expected to happen was...:
My horse to be visible.
What actually happened was...:
When I tamed a horse and put golden horse armor onto it, it disappeared.
Steps to Reproduce:
1. Tame a horse (might just happen with this one type of horse, but not certain)
2. Place a golden horse armor on it (might also trigger with other types of horse armor)
3. Note that the saddle may also have an effect.