Accessing struct list on Start() gives NullReferenceError - unity3d

Question

What in the name of god am I doing wrong here? Every time I run the game I get this: "NullReferenceException: Object reference not set to an instance of an object". I know what that means I just don't get why it is saying that?
using UnityEngine;
using System;
using System.Collections;
using System.Collections.Generic;
public class Inventory : MonoBehaviour {
public static Inventory instance;
public List<InventoryItems> INVENTORY_ITEMS = new List<InventoryItems>();
void Awake(){
instance = this;
}
void Start(){
Debug.Log(instance.INVENTORY_ITEMS); // ERROR
Debug.Log(INVENTORY_ITEMS); // ERROR
}
}
[Serializable]
public struct InventoryItems
{
public string name;
}

Answer 1

This is how you should write this code:
using UnityEngine;
using System;
using System.Collections;
using System.Collections.Generic;
public class Inventory : MonoBehaviour {
public static Inventory instance;
public List<InventoryItems> INVENTORY_ITEMS;//do not initialize here
void Awake(){
instance = this;
INVENTORY_ITEMS = new List<InventoryItems>();//init here instead
}
void Start(){
Debug.Log(instance.INVENTORY_ITEMS); //no ERROR
Debug.Log(INVENTORY_ITEMS); //no ERROR
}
}
[Serializable]
public struct InventoryItems
{
public string name;
}
Added note:
The reason for this error is that the value of a public serializable member in monobehaviour is being read from the editor (inspector) overwriting any value being assigned to it prior to Awake.
I suggest either change the list accessor to internal, or make it a property, or keep it public but let inspector handle the initialization and adding the initial elements.
Added another note:
According to Programmer and Uri Popov, your original code most certainly will work on unity 5.4 and later.