I placed a sticky piston beside a dirt block, and a rail on top of that. Placing a redstone torch beside the piston caused it to push the block and the rail to pop off. Removing the torch, expecting it to cause the piston to contract again, caused the crash. Reloading and trying again WITHOUT the rail causes no crash. Other objects, such as torches, don't seem to cause it, only rails.
MC-7622 Snapshot Crash when trying to break sugar cane