Spawning Crashes Unity

I am writing a script to randomly spawn a planet across the screen. However, when this script runs Unity crashes (It does not respond).

     public float ScreenXMin;
     public float ScreenXMax;
     public float ScreenYMin;
     public float ScreenYMax;
     private Vector2 SpawnPlace;
 
     public GameObject planet;
 
     private float PlanNum;
 
     private int i;
 
     // Use this for initialization
     void Start () {
         ScreenXMax = Screen.height;
         ScreenYMax = Screen.width;
 
         ScreenXMin = 0;
         ScreenYMin = 0;
 
 
         SpawnPlace.x = Random.Range(ScreenXMin, ScreenXMax);
         SpawnPlace.y = Random.Range(ScreenYMin, ScreenYMax);
 
         PlanNum = Random.Range(4, 8);
 
         while (i != PlanNum)
         {
             Instantiate(planet, SpawnPlace, transform.rotation);
         }
     }
 }