Instantiation Problem

Hello guys. I am currently facing a problem with instantiating a prefab. First I am instantiating the prefab from an array. Then the method SpawnCoin accepts an object[] and instantiates the same prefab. This is the code:

 public static GameObject CoinPrefab
 public static GameObject[] SpawnedCoins = new GameObject[7];
 
 void Start ()
     {
     object[,] coinsfromarray = Coins.GetCoins();
     for (int i = 1; i < 6; i++) 
             {
             SpawnedCoins [i] = Instantiate (CoinPrefab, (Vector3)coinsfromarray [i, 1], CoinPrefab.transform.rotation);
     }
   }

 public static void SpawnCoin(object[] anothercoin)
 {
        SpawnedCoins[6] = Instantiate(CoinPrefab, (Vector3)anothercoin[1], CoinPrefab.transform.rotation);
     }
 }

The first coins are instantiated as they are supposed to. However, when the SpawnCoin method is called, I get this error: NullReferenceException: Object reference not set to an instance of an object CoinSpawner.SpawnCoin

I have used Debug.Log and anothercoin[] is not null. I have also tried using a new GameObject instead of SpawnedCoins[6]. I can't get it to work. Any thoughts?