Game crashing when loading in boats with foxes

I travelled over 6000 blocks to get the fox. After multiple attempts of getting one home because they despawned when I saved and quitted. about 1500 blocks from home, the game crashed. It happened a few more times, I could see the fox only once out of the 3 times a loaded in the game before the game crashed. I was faced with this message: Error: java.lang.NullPointerException: Ticking entity

 

Please fix this Mojang.