Potential packet fix

api/src/main/java/net/jitse/npclib/internal/NPCBase.java

@@ -41,6 +41,7 @@ public abstract class NPCBase implements NPC, NPCPacketHandler {
     protected UUID uuid = new UUID(new Random().nextLong(), 0);
     protected String name = uuid.toString().replace("-", "").substring(0, 10);
     protected GameProfile gameProfile = new GameProfile(uuid, name);
+    protected boolean created = false;
 
     protected NPCLib instance;
     protected List<String> text;
@@ -177,7 +178,7 @@ public abstract class NPCBase implements NPC, NPCPacketHandler {
 
     @Override
     public boolean isShown(Player player) {
-        if (player == null) return false;
+        Objects.requireNonNull(player, "Player object cannot be null");
         return shown.contains(player.getUniqueId()) && !autoHidden.contains(player.getUniqueId());
     }
 
@@ -190,9 +191,15 @@ public abstract class NPCBase implements NPC, NPCPacketHandler {
     @Override
     public NPC create() {
         createPackets();
+        this.created = true;
         return this;
     }
 
+    @Override
+    public boolean isCreated() {
+        return created;
+    }
+
     public void onLogout(Player player) {
         getAutoHidden().remove(player.getUniqueId());
         getShown().remove(player.getUniqueId()); // Don't need to use NPC#hide since the entity is not registered in the NMS server.