Consider repair cost when checking ItemMeta emptiness. Fixes BUKKIT-5304

src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaItem.java

@@ -421,7 +421,7 @@ class CraftMetaItem implements ItemMeta, Repairable {
 
     @Overridden
     boolean isEmpty() {
-        return !(hasDisplayName() || hasEnchants() || hasLore() || hasAttributes());
+        return !(hasDisplayName() || hasEnchants() || hasLore() || hasAttributes() || hasRepairCost());
     }
 
     public String getDisplayName() {