Instantiating gameobjects in an array / class problem | NullReferenceException:

Not sure what to title this but im having problem figuring out how to use a class with an array and object instantiation. This is all simplified down to show my issue. Im getting an (NullReferenceException: Object reference not set to an instance of an object) on this line

"platformArray[0].gObject = Instantiate(prefabStump, new Vector3(2,0,0), Quaternion".

If i comment that out and just do it with the "testGO" version it works fine. Any ideas? I know just enough to be dangerous. Im an artist so this programming stuff can be tricky although i think im learning quickly :) Also i duplicate posted to the forum. Hope that's not a problem.

Thanks Jesse

     [System.Serializable]
     public class Platform
     {
         public GameObject gObject;
     }
     public Platform[] platformArray;
     public GameObject prefabStump;
 
     void Start () {
         platformArray = new Platform[10];
         platformArray[0].gObject = Instantiate(prefabStump, new Vector3(2,0,0), Quaternion.identity) as GameObject;    
 
         // This works fine
         //GameObject testGO;
         //testGO = Instantiate(prefabStump, new Vector3(2,0,0), Quaternion.identity) as GameObject;    
     }