SPIGOT-5035: Error Using Virtual Merchant GUI

nms-patches/ContainerMerchant.patch

@@ -34,3 +34,12 @@
  
          int j;
  
+@@ -96,7 +112,7 @@
+     }
+ 
+     private void j() {
+-        if (!this.merchant.getWorld().isClientSide) {
++        if (!this.merchant.getWorld().isClientSide && this.merchant instanceof Entity) { // CraftBukkit - SPIGOT-5035
+             Entity entity = (Entity) this.merchant;
+ 
+             this.merchant.getWorld().a(entity.locX, entity.locY, entity.locZ, this.merchant.eb(), SoundCategory.NEUTRAL, 1.0F, 1.0F, false);