Prevent Unity From Loading The Next Scene After Getting to the Final Scene

I’m a beginner in Unity, I wrote a script that will load the next scene whenever monsters in a scene are dead. The script is working fine. Here’s my script.

public void Update() {     if (MonstersAreAllDead())         GoToNextLevel();  }      //Loads The next Level After all the monsters are Confirmed Dead  private void GoToNextLevel() {     SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex + 1);      }  

However, I only have two scenes in my game and When Unity gets to the final scene, it displays an error since there is not next scene to load to.

Scene with build index: 2 couldn't be loaded because it has not been added to the build settings. To add a scene to the build settings use the menu File->Build Settings... UnityEngine.SceneManagement.SceneManager:LoadScene (int) LevelController:GoToNextLevel () (at Assets/Scripts/LevelController.cs:39) LevelController:Update () (at Assets/Scripts/LevelController.cs:30) 

My question. How do I tell unity that it should stop trying to load the next scene and instead Display a message to the user? The message displayed can be something like "This is the final scene".

Thank you all in advance for your answers.