add null check to getEntity API

Spigot-Server-Patches/0122-Add-getEntity-by-UUID-API.patch

@@ -1,14 +1,14 @@
-From 88d6d362e1437fc065603bbbb558448ff2443d52 Mon Sep 17 00:00:00 2001
+From d229df3e11a546bfc6fc7016a72633c4efbcec02 Mon Sep 17 00:00:00 2001
 From: DemonWav <demonwav@gmail.com>
 Date: Wed, 30 Mar 2016 01:20:11 -0500
 Subject: [PATCH] Add getEntity by UUID API
 
 
 diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
-index 058735e..0c037ff 100644
+index 058735e..06dec17 100644
 --- a/src/main/java/net/minecraft/server/MinecraftServer.java
 +++ b/src/main/java/net/minecraft/server/MinecraftServer.java
-@@ -1622,4 +1622,17 @@ public abstract class MinecraftServer implements Runnable, ICommandListener, IAs
+@@ -1622,4 +1622,20 @@ public abstract class MinecraftServer implements Runnable, ICommandListener, IAs
          return (Bukkit.getServer() instanceof CraftServer) ? ((CraftServer) Bukkit.getServer()).getServer() : null;
      }
      // CraftBukkit end
@@ -17,6 +17,9 @@ index 058735e..0c037ff 100644
 +    public Entity getEntity(UUID uuid) {
 +        Entity entity;
 +        for (WorldServer world : worldServer) {
++            if (world == null) {
++                continue;
++            }
 +            entity = world.getEntity(uuid);
 +            if (entity != null && !entity.dead) {
 +                return entity;