When right clicking on a chest in the world with a minecart, a player got kicked for "internal server error" and spat out an error in the server console

Error report + full mods list:
http://puu.sh/hjMSe/b23d5bafea.txt

Steps to reproduce:

1. get above mods
2. place chest in world
3. right click with minecart in hand
4. probably be kicked for "internal server error"

Also running on forge 1352

Cannot reproduce with just Railcraft, probably a broken core mod's fault. I can attempt to add a null check, but being unable to reproduce it I can't be certain that I'm null checking the correct object.