NullReferenceException: Object reference not set to an instance of an object C#

NullReferenceException: Object reference not set to an instance of an object
SaludEnemigo1.OnTriggerEnter2D (UnityEngine.Collider2D collider) (at Assets/Scripts/SaludEnemigo1.cs:62)

This is my entire error, I don’t know what to do. Anybody can help me, please?

Those are my codes.

using UnityEngine;
using System.Collections;

public class ScoreScript : MonoBehaviour {


	// Interfaz Grafica 

	public GUIText scoreText;
	private int score;


	void Start () {
		score = 0;
		UpdateScore ();
	}
	
	public void AddScore (int newScoreValue)
		
	{
		score += newScoreValue;
		UpdateScore ();
	}
	
	
	
	void UpdateScore ()
	{
		scoreText.text = "Score: " + score;
	}

}

using UnityEngine;
using System.Collections;

/// Comportamiento de la salud de los objetos

public class SaludEnemigo1 : MonoBehaviour {
	
	
	/// Numero de puntos de salud
	
	public int ps = 2;
	
	private GameObject Enemigo1;
	private ScoreScript scoreScript;
	public int ScoreValue;
	
	
	/// Es jugador o enemigo?
	
	public bool esEnemigo = true;

	// LLamamos el script score y el tag enemigo1
	
	void start ()
	{
		GameObject scoreScriptObject = GameObject.FindGameObjectWithTag ("ScoreScript");
		if (scoreScriptObject != null) {
			scoreScript = scoreScriptObject.GetComponent <ScoreScript> ();
		}
		if (scoreScript == null) {
			Debug.Log ("No se puede encontrar ScoreScript");
		}

		Enemigo1 = GameObject.FindWithTag ("Enemigo1");
		if (Enemigo1 == null) {
						Debug.Log ("No se encuentra a enemigo1");
				}
	}


	
	void OnTriggerEnter2D(Collider2D collider)
	{
		//Es un disparo?
		Disparar disparo = collider.gameObject.GetComponent<Disparar>();
		if (disparo != null)
		{
			// Revisamos si es enemigo o compañero
			if (disparo.esDisparoEnemigo != esEnemigo)
			{
				ps -= disparo.daño;
				
				// Destruimos el disparo
				// No colocar solo Destroy()
				//sino eliminara el Script
				Destroy(disparo.gameObject);
				
				if (ps <= 0)
				{
					// Muerto + EfectoEspecial de particulas, += score

					scoreScript.AddScore(ScoreValue);
					EfectosEspecialesScript.Instancia.Explosion(transform.position);
					EfectosDeSonido.Instancia.ReproducirSonidoExplosion();
					Destroy(gameObject); 
					
				}
				
			}
		}
	}
	void OnCollisionEnter2D(Collision2D coll)
	{
		if (coll.gameObject.tag == "Player")
			ps = 0; 
		EfectosEspecialesScript.Instancia.ExplosionAsteroide(transform.position);
		Destroy(Enemigo1); 
	}
}

I want the line “scoreScript.AddScore(ScoreValue);” to work but I don’t know what to do, I’ve searched for 3 h and nothing. Maybe the error it provide in console is for the method I call the script? If it’s that, how can I do the best way for instance?

Thanks a lot for your help!

In

void start () 

Start must begin with capital letter. C# is case-sensitive, so your start() function isn’t executed at all.

+1 for JustFun…and since start is not being called, your variables are not being initialized.