Paper/Spigot-Server-Patches/0409-Fix-AssertionError-when-player-hand-set-to-empty-typ.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Lukasz Derlatka <toranktto@gmail.com>
Date: Mon, 11 Nov 2019 16:08:13 +0100
Subject: [PATCH] Fix AssertionError when player hand set to empty type

Fixes an AssertionError when setting the player's item in hand to null or a new ItemStack of Air in PlayerInteractEvent
Fixes GH-2718

diff --git a/src/main/java/net/minecraft/server/EntityLiving.java b/src/main/java/net/minecraft/server/EntityLiving.java
index 24594aa0e9b8741811acfc9f84f4db7552832bd2..aada8d3b08b437f81f68f8e988412c1071287d54 100644
--- a/src/main/java/net/minecraft/server/EntityLiving.java
+++ b/src/main/java/net/minecraft/server/EntityLiving.java
@@ -1891,6 +1891,7 @@ public abstract class EntityLiving extends Entity {
         return this.getEquipment(EnumItemSlot.OFFHAND);
     }
 
+    public ItemStack getItemInHand(EnumHand enumhand) { return this.b(enumhand); } // Paper - OBFHELPER
     public ItemStack b(EnumHand enumhand) {
         if (enumhand == EnumHand.MAIN_HAND) {
             return this.getEquipment(EnumItemSlot.MAINHAND);
diff --git a/src/main/java/net/minecraft/server/PlayerConnection.java b/src/main/java/net/minecraft/server/PlayerConnection.java
index f00653dfe7a769992069582f1743b477edb47eb9..71d045ee00d1f172d88f076d15cf82bae2527ae8 100644
--- a/src/main/java/net/minecraft/server/PlayerConnection.java
+++ b/src/main/java/net/minecraft/server/PlayerConnection.java
@@ -1430,6 +1430,10 @@ public class PlayerConnection implements PacketListenerPlayIn {
             if (cancelled) {
                 this.player.getBukkitEntity().updateInventory(); // SPIGOT-2524
             } else {
+                // Paper start
+                itemstack = this.player.getItemInHand(enumhand);
+                if (itemstack.isEmpty()) return;
+                // Paper end
                 this.player.playerInteractManager.a(this.player, worldserver, itemstack, enumhand);
             }
             // CraftBukkit end