Re-added the patch for LivingExperienceDropEvent and enable it for dragons (#8388)

src/main/java/net/minecraftforge/event/entity/living/LivingExperienceDropEvent.java

@@ -1,6 +1,6 @@
 /*
  * Minecraft Forge
- * Copyright (c) 2016-2021.
+ * Copyright (c) 2016-2022.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -23,6 +23,8 @@ import net.minecraft.world.entity.LivingEntity;
 import net.minecraft.world.entity.player.Player;
 import net.minecraftforge.eventbus.api.Cancelable;
 
+import javax.annotation.Nullable;
+
 /**
  * Event for when an entity drops experience on its death, can be used to change
  * the amount of experience points dropped or completely prevent dropping of experience
@@ -31,12 +33,12 @@ import net.minecraftforge.eventbus.api.Cancelable;
 @Cancelable
 public class LivingExperienceDropEvent extends LivingEvent
 {
-    private final Player attackingPlayer;
+    @Nullable private final Player attackingPlayer;
     private final int originalExperiencePoints;
 
     private int droppedExperiencePoints;
 
-    public LivingExperienceDropEvent(LivingEntity entity, Player attackingPlayer, int originalExperience)
+    public LivingExperienceDropEvent(LivingEntity entity, @Nullable Player attackingPlayer, int originalExperience)
     {
         super(entity);
 
@@ -54,6 +56,10 @@ public class LivingExperienceDropEvent extends LivingEvent
         this.droppedExperiencePoints = droppedExperience;
     }
 
+    /**
+     * @return The player that last attacked the entity and thus caused the experience. This can be null, in case the player has since logged out.
+     */
+    @Nullable
     public Player getAttackingPlayer()
     {
         return attackingPlayer;