SPIGOT-4860: Cancelling InventoryOpenEvent on MerchantInventory prevents re-opening

nms-patches/InventoryMerchant.patch

@@ -14,7 +14,7 @@
  
  public class InventoryMerchant implements IInventory {
  
-@@ -12,6 +19,45 @@
+@@ -12,6 +19,46 @@
      public int selectedIndex;
      private int e;
  
@@ -32,6 +32,7 @@
 +
 +    public void onClose(CraftHumanEntity who) {
 +        transaction.remove(who);
++        merchant.setTradingPlayer((EntityHuman) null); // SPIGOT-4860
 +    }
 +
 +    public List<HumanEntity> getViewers() {