--- ../work/decompile-8eb82bde/net/minecraft/server/EnchantmentThorns.java	2014-12-10 15:53:01.980344940 +1100
+++ src/main/java/net/minecraft/server/EnchantmentThorns.java	2014-12-10 15:52:50.688364236 +1100
@@ -29,7 +29,7 @@
         Random random = entityliving.bb();
         ItemStack itemstack = EnchantmentManager.a(Enchantment.THORNS, entityliving);
 
-        if (a(i, random)) {
+        if (entity != null && a(i, random)) { // CraftBukkit
             entity.damageEntity(DamageSource.a(entityliving), (float) b(i, random));
             entity.makeSound("damage.thorns", 0.5F, 1.0F);
             if (itemstack != null) {