One component in Array which is a class resets itself to null.

I don't even know how to formulate a question since I have 0 idea why this error is occurring. My observation, after 5 quadrillion Debug.Log statements, is that somewhere along storing the class array which includes class, the class value becomes null. I have checked this through confirming whether or not the values actually change. It's better explained through code.

Inventory.cs: handles inventory storage as well as GUI display.

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

 public class Inventory : MonoBehaviour {

     public ItemClass holdingNow;
     inventoryItems[] inventoryStuff = new inventoryItems[5];
     public GameObject[] itemIconGUI = new GameObject[5];
     public GameObject[] itemNumberGUI = new GameObject[5];

     // Use this for initialization
     void Start () {
         Debug.Log ("start");
         inventoryStuff [0] = new inventoryItems (null, "", 0);
         inventoryStuff [1] = new inventoryItems (null, "", 0);
         inventoryStuff [2] = new inventoryItems (null, "", 0);
         inventoryStuff [3] = new inventoryItems (null, "", 0);
         inventoryStuff [4] = new inventoryItems (null, "", 0);
     }
     
     // Update is called once per frame
     void Update () {
         //update gui display
         for (int i = 0; i < 5; i++) {
             Debug.Log ("updating GUI");
             itemIconGUI [i].GetComponent<Image> ().sprite = Sprite.Create (inventoryStuff [i].iClass.itemTexture, new Rect (0, 0, 30, 30), new Vector2 (0.5f, 0.5f));

             itemNumberGUI [i].GetComponent<Text> ().text = inventoryStuff [i].numberOfItem.ToString ();
         }


     }

     public void AddItem (ItemClass itemClass) {
         for (int i = 0; i <= 4; i++) {
             Debug.Log (inventoryStuff [i].iClass + ", " + inventoryStuff [i].item + ", " + inventoryStuff [i].numberOfItem);
         }
         //already exists and stackable
         for (int i = 0; i <= 4; i++) {
             if (inventoryStuff [i].item == itemClass.itemName) {
                 Debug.Log (itemClass);
                 if (inventoryStuff [i].numberOfItem < itemClass.maxStack) {
                     inventoryStuff [i].iClass = itemClass;
                     inventoryStuff [i].numberOfItem += 1;
                     Debug.Log ((ItemClass)inventoryStuff [i].iClass);
                     return;
                 }
             }
         }
         int firstEmptySlot = emptySlot ();
         if (firstEmptySlot >= 0) {
             inventoryStuff [firstEmptySlot].iClass = (ItemClass)itemClass;
             inventoryStuff [firstEmptySlot].item = itemClass.itemName;
             inventoryStuff [firstEmptySlot].numberOfItem = 1;
             return;
         }
         if (firstEmptySlot < 0) {
             Debug.Log ("inventory full");
             return;
         }
     }

     int emptySlot() {
         for (int i = 0; i <= 4; i++) {
             if (inventoryStuff [i].item == "") {
                 return i;
             }
         }
         return -1;
     }

     public class inventoryItems {
         public ItemClass iClass;
         public string item;
         public int numberOfItem;

         public inventoryItems(ItemClass cla, string ite, int num) {
             iClass = cla;
             item = ite;
             numberOfItem = num;
         }
     }
 }

ItemInteraction.cs: handles interactions between player and item tagged objects.

 using UnityEngine;
 using System.Collections;

 public class ItemInteraction : MonoBehaviour {

     private Vector3 position;
     public GameObject inventoryManager;

     void Start() {
         position = new Vector3(Screen.width/2, Screen.height/2);
     }
     
     void Update () {
         if(Input.GetKeyDown(KeyCode.E) && !UnityEngine.EventSystems.EventSystem.current.IsPointerOverGameObject()) {
             Collect ();
         }
     }

     void Collect () {
         Ray interactRay = Camera.main.ScreenPointToRay (position);
         RaycastHit interactionInfo;
         if (Physics.Raycast (interactRay, out interactionInfo, 100)) {
             GameObject collectableObject = interactionInfo.collider.gameObject;
             if (collectableObject.tag == "item") {
                 Destroy (collectableObject);
                 inventoryManager.GetComponent<Inventory> ().AddItem (collectableObject.GetComponent<ItemClass> ());
                 Debug.Log (collectableObject.GetComponent<ItemClass> ());
             }
         }
     }
 }

ItemClass.cs: base class for items.

 using UnityEngine;
 using System.Collections;

 public class ItemClass : MonoBehaviour {

     public string itemName = "item";
     public int maxStack = 30;
     public Texture2D itemTexture;

     public virtual void Use() {

     }

     public virtual void Trash() {

     }
 }

I suspect that the storing of the data type ItemClass is where everything is going terribly wrong, though I don't see why because the class array's class specifies the ItemClass.