NullRefException at Index 0 in list

So I have a Rhythm Controller (while using RhythmTool) and in this controller I have this public list called "items" that's apart of a class. Every item that is added to that list is manipulated by the for-loop below to move the object at the speed of the low frequency frames (Beat, bass, etc).

  //move the objects at the speed of the frame.
         foreach (ItemScript item in items)
         {
             for (int i = rhythmTool.CurrentFrame; i < item.Index; i++)
             {
                 variableSpeed += low[i].magnitudeSmooth * .2f;
             }
 
             variableSpeed -= (low[rhythmTool.CurrentFrame].magnitudeSmooth * .2f) * rhythmTool.Interpolation;
 
             position.y += variableSpeed;
             item.gameObject.transform.position = vanishingPoint;
 
             if (rhythmTool.CurrentFrame >= item.Index)
                 toRemove.Add(item);
         }
 
         foreach (ItemScript item in toRemove)
         {
             items.Remove(item);
             item.gameObject.SetActive(false);
         }

When I activate objects through a different class, I want to add them to the list so that they can be manipulated by the for loop above. I do so using this:

  public void SpawnObject()
         {
             GameObject obj = ObjectPoolerScript.current.GetPooledObject();
             if (obj == null) return;
             obj.transform.position = transform.position;
             obj.transform.rotation = transform.rotation;
             RhythmController.current.items.Add(obj.GetComponent<ItemScript>());
             obj.SetActive(true);
         }

The problem I'm getting is that when I try to add an object to the items list, nothing happens at run time. The Item's list remains at 0 for its Count. However when I add one to the size of the list (or the Count variable). They are added to the list without any problem. Because of the code above though, I get a NullReferenceException due to there being object at the index of items.

How would I go about making sure that the first item added to the list is at the index from the start?