Hello, I am not exactly positive how or why this crash happens and the actual contents of the crash log are almost zero help. The only way I am able to reproduce this simply by running around until new biomes load into the world, and in this case Abyssalcraft. I have noticed it mainly when demon cows are interacted with or load onto the screen, but that is about the only thing I can connect to this.

http://pastebin.com/ZRhnM3Rd
AbyssalCraft-1.9-1.9.1.6
AbyssalCraft Integration-1.9-1.4.3
Forge 1907

Ran around the world after removing the mods, unable to reproduce the crash.

Just as i said that, I crashed. This looks like it is not related to your mod. My apologies.