ArgumentException: The prefab you want to instantiate is null.

Hey guys,

I'm running into a problem. I have a script which instantiates a prefab, like this:

 public class SegmentScript : MonoBehaviour {
 
  public GameObject bar_piece;
  private int start_height;
  private int end_height;
  private int score;
  private GameObject[] pieces;
  private Vector3 start_location;
  
  // Use this for initialization
  public void Start () {
  
  pieces = new GameObject[10];
  
  AddPieces(start_height, end_height);
  }
  
  public void AddPieces(int start, int end){
  
  for(int i = start;i<end;i++){
  Vector3 piece_location = start_location;
  piece_location.y = i;
  
  GameObject new_piece = Instantiate(bar_piece, piece_location, Quaternion.Euler(0,0,0)) as GameObject;
  pieces[i] = new_piece;
  }
  }
 }

Now, when I select the script in the inspector, I can drag and drop a prefab to the bar_piece slot. During runtime, I add this script through another script using the AddComponent function.

But somehow the prefab slot for bar_piece is empty again and I get the ArgumentException.

The weirdest part is that another script uses the exact same method to instantiate an object, but that works fine.