Put the summary of the bug you're having here

What I expected to happen was...:
I was expecting nothing out of the ordinary to happen, when travelling on a horse.

What actually happened was...:
What happened was that the horse got stuck in a block when trying to ride it in elevated landscape.

Steps to Reproduce:
1. Mount a horse
2. Ride the horse in elevated landscape, where the landscape only increases with one block of height.
3. The bug should now appear, after trying to ride the horse up a couple of blocks.