Question Object Reference not set to an instance

I got a unity project with multiple scenes, and I got it to pretty much it just plays until I call it quit. However, after one loop (game menu, then game play, then game over (which is where I save the score of the player)), when I try to go the game play scene again, I got the "Object reference not set to an instance of an object". Does anyone know why?

This is where it led

Code (CSharp):

1. foreach(Enemy enemy in enemyScripts)
2.         {
3.             // If the script object is not null, its game object is still in the scene.
4.             if (enemy != null)
5.             {
6.                 // Tell the enemy to perform its movement behavior.
7.                 enemy.Move(player.transform);
8.  
9.                 // Add the current script to the new script list.
10.                 newScripts.Add(enemy);
11.             }
12.         }

me to:

 

Doesn't matter. Answer is ALWAYS the same, ALWAYS.

How to fix a NullReferenceException error

https://forum.unity.com/threads/how-to-fix-a-nullreferenceexception-error.1230297/

Three steps to success:
- Identify what is null <-- any other action taken before this step is WASTED TIME
- Identify why it is null
- Fix that

 

So I have fiddle around with it, and it seems that when I tried to go to the play scene again, for some reason, despite that the player game object is linked to the enemy manager, the enemy manager still could not see the player.

 

Make sure you're doing that correctly. No asset (such as a prefab) on disk can hold a reference to anything in the scene... only the other way around.