[SEVERE] java.lang.Throwable
13:08:57 [SEVERE]       at net.minecraft.server.ChunkProviderServer.getOrCreateChunk(ChunkProviderServer.java:112)
13:08:57 [SEVERE]       at net.minecraft.server.World.getChunkAt(World.java:333)
13:08:57 [SEVERE]       at net.minecraft.server.World.b(World.java:2369)
13:08:57 [SEVERE]       at net.minecraft.server.EntityLiving.d(EntityLiving.java:916)
13:08:57 [SEVERE]       at net.minecraft.server.EntityMonster.d(EntityMonster.java:27)
13:08:57 [SEVERE]       at net.minecraft.server.EntityZombie.d(EntityZombie.java:38)
13:08:57 [SEVERE]       at net.minecraft.server.EntityPigZombie.d(EntityPigZombie.java:54)
13:08:57 [SEVERE]       at net.minecraft.server.EntityLiving.w_(EntityLiving.java:297)
13:08:57 [SEVERE]       at net.minecraft.server.EntityMonster.w_(EntityMonster.java:31)
13:08:57 [SEVERE]       at net.minecraft.server.EntityPigZombie.w_(EntityPigZombie.java:32)
13:08:57 [SEVERE]       at net.minecraft.server.World.entityJoinedWorld(World.java:1253)
13:08:57 [SEVERE]       at net.minecraft.server.WorldServer.entityJoinedWorld(WorldServer.java:107)
13:08:57 [SEVERE]       at net.minecraft.server.World.playerJoinedWorld(World.java:1235)
13:08:57 [SEVERE]       at net.minecraft.server.World.tickEntities(World.java:1142)
13:08:57 [SEVERE]       at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:518)
13:08:57 [SEVERE]       at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:425)
13:08:57 [SEVERE]       at net.minecraft.server.ThreadServerApplication.run(SourceFile:457)