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/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index e45690b6197335ed1c07fa04c39b311b401724d7..2b79413bb8a592a7b7093e11d3a0cce895286c8f 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -1706,6 +1706,10 @@ public class ServerGamePacketListenerImpl implements ServerGamePacketListener {
                 this.player.getBukkitEntity().updateInventory(); // SPIGOT-2524
                 return;
             }
+            // Paper start
+            itemstack = this.player.getItemInHand(enumhand);
+            if (itemstack.isEmpty()) return;
+            // Paper end
             InteractionResult enuminteractionresult = this.player.gameMode.useItem(this.player, worldserver, itemstack, enumhand);
 
             if (enuminteractionresult.shouldSwing()) {
diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
index f8917123547615dd624e3e428ec1bf6450c7b7d8..b49d4772932a58852b3195f5f56ff93dbcabf766 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -2153,6 +2153,7 @@ public abstract class LivingEntity extends Entity {
         return predicate.test(this.getMainHandItem().getItem()) || predicate.test(this.getOffhandItem().getItem());
     }
 
+    public final ItemStack getItemInHand(InteractionHand enumhand) { return this.getItemInHand(enumhand); } // Paper - OBFHELPER
     public ItemStack getItemInHand(InteractionHand hand) {
         if (hand == InteractionHand.MAIN_HAND) {
             return this.getItemBySlot(EquipmentSlot.MAINHAND);