Horse randomly rears occasionally while riding without player influence

Every so often after a (usually long) period of time, a tamed horse you are riding on will rear on its hind legs even if you do not use the jump button.

To test:

1. Ride a tamed and saddled horse
2. Wait until you see it rear on its hind legs, this also temporarily pauses any horse movement when riding the horse
3. This also occurs when the horse has NoAI