After further checking the bug reports, this is a duplicate of https://bugs.mojang.com/browse/MC-108367, which may be erroniously marked as a duplicated of a https://bugs.mojang.com/browse/MC-108358 as the crash in the latter did not occur when a piston extension were being ticked. Anyway sorry for wasting your time 😉, edit: nvm, both of them are the same too 😉
I had this very same issue, I tested it and it did not occure on 14w11b but did on 14w17/18 a/b, it did however get fixed after a complete reinstallation of my unmodded game.
Filip Törnqvist
After further checking the bug reports, this is a duplicate of https://bugs.mojang.com/browse/MC-108367, which may be erroniously marked as a duplicated of a https://bugs.mojang.com/browse/MC-108358 as the crash in the latter did not occur when a piston extension were being ticked. Anyway sorry for wasting your time 😉,
edit: nvm, both of them are the same too 😉