Sorry I broke your mod. Happens when switching from one shell to another when they are underground. Crash happens when reentering the earth. Any more info you need to maybe help? I think the error may be mojangs fault though because of the lines its in. idk if there is a work around though or not.

---- Minecraft Crash Report ----
// I feel sad now :(

Time: 1/3/16 11:21 PM
Description: Unexpected error

java.lang.NullPointerException: Unexpected error
at net.minecraft.client.renderer.ItemRenderer.func_78446_a(ItemRenderer.java:616)
at net.minecraft.client.renderer.ItemRenderer.func_78447_b(ItemRenderer.java:565)
at net.minecraft.client.renderer.EntityRenderer.func_78476_b(EntityRenderer.java:962)
at net.minecraft.client.renderer.EntityRenderer.func_78471_a(EntityRenderer.java:1720)
at net.minecraft.client.renderer.EntityRenderer.func_78480_b(EntityRenderer.java:1301)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1001)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:898)
at net.minecraft.client.main.Main.main(SourceFile:148)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)