craftbukkit/nms-patches/net/minecraft/world/item/ItemEnderEye.patch

--- a/net/minecraft/world/item/ItemEnderEye.java
+++ b/net/minecraft/world/item/ItemEnderEye.java
@@ -86,7 +86,11 @@
 
                     entityendersignal.setItem(itemstack);
                     entityendersignal.signalTo(blockposition);
-                    world.addFreshEntity(entityendersignal);
+                    // CraftBukkit start
+                    if (!world.addFreshEntity(entityendersignal)) {
+                        return new InteractionResultWrapper(EnumInteractionResult.FAIL, itemstack);
+                    }
+                    // CraftBukkit end
                     if (entityhuman instanceof EntityPlayer) {
                         CriterionTriggers.USED_ENDER_EYE.trigger((EntityPlayer) entityhuman, blockposition);
                     }