Put the summary of the bug you're having here: Horse disappears after dismounting sometimes

What I expected to happen was...:
My horse would still be there when I dismounted.

What actually happened was...:
My horse disappeared when I dismounted or got kicked off when going into deep water.

Steps to Reproduce:
1. Mount a horse
2. Dismount the horse
3. The horse disappears until you exit and come back into the game. Happens both on minecraft realms and singleplayer.