Crash: Tick Entity

The game crashed a short time after entering the overworld (I logged on in the Nether). This happened in both the 1.8.1-pre5 and 1.8.1 version. I attached both crash dumps for reference.
It seems to be related to a moving poppy in the spawn chunks. I do have an iron golem farm and a dispenser shooting poppys into a nether portal to keep the chunks loaded.