Object reference not set to an instance of an object?

Questions & Answers
1

I’m trying to make an instance and it isn’t happening.

Error I’m getting :
NullReferenceException: Object reference not set to an instance of an object
Score.AddPoint () (at Assets/Score.cs:11)
ScorePoint.OnTriggerEnter2D (UnityEngine.Collider2D collider) (at Assets/ScorePoint.cs:8)

   using UnityEngine;
    using System.Collections;
    
    public class Score : MonoBehaviour {
    
    	static int score = 0;
    	static int highScore = 0;
    	static Score instance;
    
    	static public void AddPoint(){
    			if (instance.bird.dead)
    						return;
    		score++;
    		if (score > highScore) {
    						highScore = score;
    				}
    	}
    
    	BirdMovement bird;
    
    	void Start(){
    		instance = this;
    				score = 0;
    				GameObject player_go = GameObject.FindGameObjectWithTag ("PlayerBird");
    				if (player_go == null) {
    						Debug.LogError ("Could not find an object with tag 'Plyaerbird'!");
    				}
    				bird = player_go.GetComponent<BirdMovement> ();
    				highScore = PlayerPrefs.GetInt ("highScore", 0);
    		}
    
    
    
    
    	void OnDestroy(){
    		instance = null;	
    		PlayerPrefs.SetInt ("highScore", highScore);
    	}
    
    
    	void Update () {
    		guiText.text = "" + score;
    	}
    }
2

The warning is telling you the problem. Your instance variable is null. Because you assign instance in Start and clear it in Destroy, you must be calling AddPoint before your an instance of your Score object is created or after it is destroyed.

PS - You should check out static classes for simple singletons like this. They can be simpler and use less memory/CPU than a custom component.