SPIGOT-2889: Error cancelling creative InventoryClickEvent

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

paper-server/nms-patches/PlayerConnection.patch

@@ -1453,7 +1453,7 @@
 +                    // Reset the slot
 +                    if (packetplayinsetcreativeslot.a() >= 0) {
 +                        this.player.playerConnection.sendPacket(new PacketPlayOutSetSlot(this.player.defaultContainer.windowId, packetplayinsetcreativeslot.a(), this.player.defaultContainer.getSlot(packetplayinsetcreativeslot.a()).getItem()));
-+                        this.player.playerConnection.sendPacket(new PacketPlayOutSetSlot(-1, -1, null));
++                        this.player.playerConnection.sendPacket(new PacketPlayOutSetSlot(-1, -1, ItemStack.a));
 +                    }
 +                    return;
 +                }