SPIGOT-5038: Inventory.getHolder returns null for wandering traders

By: md_5 <git@md-5.net>

paper-server/nms-patches/InventoryMerchant.patch

@@ -49,7 +49,7 @@
 +    }
 +
 +    public org.bukkit.inventory.InventoryHolder getOwner() {
-+        return (merchant instanceof EntityVillager) ? (CraftAbstractVillager) ((EntityVillager) this.merchant).getBukkitEntity() : null;
++        return (merchant instanceof EntityVillagerAbstract) ? (CraftAbstractVillager) ((EntityVillagerAbstract) this.merchant).getBukkitEntity() : null;
 +    }
 +
 +    @Override