NullReferenceException: Object reference not set to an instance of an object

Hey, Im working on a inventory-system and I keep getting this error:

NullReferenceExeption: Object
reference not set to an instance of an
object Inventory.Start() (at
Assets/…/Inventory.cs:32)

I have no idea what causes it because Im pretty new to Unity and C#.
I’ve already read some other Posts but I didn’t find anything helpful.

Heres the code:

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class Inventory : MonoBehaviour {

    public GameObject slotPrefab;
    private List<GameObject> allSlots;

    public GameObject Slot1, Slot2, Slot3, Slot4, Slot5, Slot6, Slot7, Slot8, Slot9, Slot10 ,Slot11 ,Slot12 ,Slot13 ,Slot14;

    private int emptySlots;

	void Start ()
    {
        allSlots.Add(Slot1);
        allSlots.Add(Slot2);
        allSlots.Add(Slot3);
        allSlots.Add(Slot4);
        allSlots.Add(Slot5);
        allSlots.Add(Slot6);
        allSlots.Add(Slot7);
        allSlots.Add(Slot8);
        allSlots.Add(Slot9);
        allSlots.Add(Slot10);
        allSlots.Add(Slot11);
        allSlots.Add(Slot12);
        allSlots.Add(Slot13);
        allSlots.Add(Slot14);

        emptySlots = 14;
	}

	void Update () 
    {
	
	}

    public bool AddItem(Item item)
    {
        if(item.maxStack == 1)
        {
            PlaceInEmpty(item);
            return true;
        }
        return false;
    }

    private bool PlaceInEmpty(Item item)
    {
        if(emptySlots > 0)
        {
            foreach (GameObject slot in allSlots)
            {
                Slot tmp = slot.GetComponent<Slot>();

                if(tmp.IsEmpty)
                {
                    tmp.AddItem(item);
                    emptySlots--;
                    return true;
                }
            }
        }

        return false;
    }
}

Perhaps each time you create an instance of your class object you need to instantiate a new list

void Start ()
     {
         allSlots = new List<GameObject>;
         allSlots.Add(Slot1);
         allSlots.Add(Slot2);
         allSlots.Add(Slot3); ....

Its late and just finished work so I maybe off a little lol!

Give it a try, the error is basically telling you that an object hasn’t been properly referenced/created,
Is that line number 32 where the error occurs? if so its possible its the “emptySlots = 14;”

Therefore try:

this.emptySlots = 14;

I maybe way off sorry if I am!

Stewart