Horse Bug

My friend created a world and opened it to LAN. I clicked a horse to ride it, and I got the error (and was kicked from the server):
"Internal exception: java.lang.NullPointerException" and my friend had to create a new world in order for me to join.

What I expected to happen was...: To be able to ride the horse
Describe what you thought should happen here

What actually happened was...:Couldn't get on
Describe what happened here

Steps to Reproduce:
1.Create a world
2. Open to LAN (Creative Cheats On)
3. Spawn a horse (any horse)
4. Ride the horse