PaperMC/paper-server/nms-patches/net/minecraft/world/entity/projectile/EntityEnderSignal.patch

--- a/net/minecraft/world/entity/projectile/EntityEnderSignal.java
+++ b/net/minecraft/world/entity/projectile/EntityEnderSignal.java
@@ -38,8 +38,8 @@
     }
 
     public void setItem(ItemStack itemstack) {
-        if (!itemstack.a(Items.ENDER_EYE) || itemstack.hasTag()) {
-            this.getDataWatcher().set(EntityEnderSignal.DATA_ITEM_STACK, (ItemStack) SystemUtils.a((Object) itemstack.cloneItemStack(), (itemstack1) -> {
+        if (true || !itemstack.a(Items.ENDER_EYE) || itemstack.hasTag()) { // CraftBukkit - always allow item changing
+            this.getDataWatcher().set(EntityEnderSignal.DATA_ITEM_STACK, (ItemStack) SystemUtils.a(itemstack.cloneItemStack(), (itemstack1) -> { // CraftBukkit - decompile error
                 itemstack1.setCount(1);
             }));
         }
@@ -182,7 +182,7 @@
     public void loadData(NBTTagCompound nbttagcompound) {
         ItemStack itemstack = ItemStack.a(nbttagcompound.getCompound("Item"));
 
-        this.setItem(itemstack);
+        if (!itemstack.isEmpty()) this.setItem(itemstack); // CraftBukkit - SPIGOT-6103 summon, see also SPIGOT-5474
     }
 
     @Override