What is the reason for this NullReferenceException?

Questions & Answers
1

None of my other Objects seem to be able to reference the script ItemManager, every time I call for a static variable from it, it returns null.

World -
[24535-ss+(2014-03-30+at+06.09.45).png|24535]

Player -
[24536-ss+(2014-03-30+at+06.11.40).png|24536]

Here is the first (of many) places I get the error:

    NullReferenceException: Object reference not set to an instance of an object
    Inventory.Start () (at Assets/Scripts/Player/Inventory.cs:58

    Line58: ItemSlot temp = new ItemSlot(ItemManager.EMPTY.ShallowCopy());

I think it has to do with the static variable EMPTY, however I believe I have it setup correctly:

public static Item EMPTY;
	public static Item STONE;
	public static Item GRASS;
	public static Item BRICK;
	
	//************************************

	// Use this for initialization

	void Start () {
		Debug.Log ("Initalized");
		guiCon = gameObject.GetComponent ("GUIController") as GUIController;
		soundMan = gameObject.GetComponent ("SoundManager") as SoundManager;
		
		// *** Set new ***
		
		// *** Initialize Item *** 
		EMPTY = new Item("", 0 , 64, new Rect(0.25f,0.75f, 0.25f,0.25f), itemIcons, Item.ItemType.Empty,"DefaultItem");
            // MORE CODE AFTER...
2

I saved, reopened Unity, and it was suddenly working. I didn’t even change anything. Don’t know what was wrong.