Fixes dead entity dupe

src/main/java/net/minecraft/server/Entity.java

@@ -188,6 +188,7 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
     public boolean fromMobSpawner;
     public boolean spawnedViaMobSpawner; // Paper - Yes this name is similar to above, upstream took the better one
     protected int numCollisions = 0; // Paper
+    public boolean joinedWorld; // Akarin
     public void inactiveTick() { }
     // Spigot end
 

src/main/java/net/minecraft/server/EntityLiving.java

@@ -1210,7 +1210,7 @@ public abstract class EntityLiving extends Entity {
     }
 
     public void die(DamageSource damagesource) {
-        if (!this.killed) {
+        if (!this.killed && !this.joinedWorld) { // Akarin
             Entity entity = damagesource.getEntity();
             EntityLiving entityliving = this.cv();
 

src/main/java/net/minecraft/server/World.java

@@ -1550,6 +1550,7 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
             return;
         }
         // CraftBukkit end
+        entity.joinedWorld = true; // Akarin
 
         entity.N = entity.locX;
         entity.O = entity.locY;
@@ -1622,6 +1623,7 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
                 }
             }
         }
+        entity.joinedWorld = false; // Akarin
     }
 
     // Paper start - Based on method below