Repeated ClassCastException Crahses

With 1.9 moving into a bug fixing phase I decided to try to load a backup of my 1.8.7 world in the latest snapshot. While doing this I have been getting repeated (over 20) crashes from a ClassCastException: "ahw cannot be cast to ahn", and the Stacktrace is basically gibberish to me. I have included the crash reports that had different entities being ticked when the crash occurred. They were a Witch, Villager and an Enderman; although the majority of the crashes were a Villager. I don't know if it is related but I will mention that in all cases the entity being ticked had a NullPointerException under its "Entity's Vehicle:" section. I hope this gets resolved otherwise I'll have to start a new world and lose all I've made if I want to play with 1.9 features.