SPIGOT-5462: Cancelling EntitySpawnEvent takes Ender Eye from inventory

nms-patches/ItemEnderEye.patch

@@ -0,0 +1,15 @@
+--- a/net/minecraft/server/ItemEnderEye.java
++++ b/net/minecraft/server/ItemEnderEye.java
+@@ -61,7 +61,11 @@
+ 
+                     entityendersignal.b(itemstack);
+                     entityendersignal.a(blockposition);
+-                    world.addEntity(entityendersignal);
++                    // CraftBukkit start
++                    if (!world.addEntity(entityendersignal)) {
++                        return new InteractionResultWrapper(EnumInteractionResult.FAIL, itemstack);
++                    }
++                    // CraftBukkit end
+                     if (entityhuman instanceof EntityPlayer) {
+                         CriterionTriggers.m.a((EntityPlayer) entityhuman, blockposition);
+                     }