Problem for moving an object with a button

Hye

I try to move an object only if i use "steroid" but the i have this error :

NullReferenceException: Object reference not set to an instance of an object Interact.OnGUI () (at Assets/Script/Interact.cs:57)

I'm a beginner, i make this code with some differents tutorials

This is my code

using UnityEngine; using System.Collections;

public class Interact: MonoBehaviour {

public GUIText texteTarget;

private bool selected = false;

public Transform target;

public bool steroide;

public Event e = Event.current;

public float steroideTimer;

public float coolDown;

 // Use this for initialization
 void Start () 
 {
     steroideTimer = 0;
     coolDown = 2.0f;
     steroide= false;
 }
 
 // Update is called once per frame
 void Update () 
 {
     renderer.material.color = Color.white;
     selected = false;
     
     if(steroideTimer > 0)
     {
         steroideTimer -= Time.deltaTime;
     }
     if (steroideTimer < 0)
     {
         steroideTimer = 0;
     }
     
     if(Input.GetKeyUp("1"))
     {
         if(steroideTimer == 0)
         {
             Steroide();
             steroideTimer = coolDown;
         }
     }

 }
 
 public void OnLookEnter()
 {
     renderer.material.color = Color.red;
     texteTarget.text = "Press E to interact";
     selected = true;
 }
 
 void OnGUI()
 {
     if(e.isKey && e.character == 'e' && selected)
     {
         if (steroide == true)
         target.Translate(5,1,0);
     }
 }
 
 void Steroide()
 {
     if(Input.GetKeyDown("1"))
     {
         steroide = true;
     }
 }

}