Weird MissingReferenceException

Iam getting a weird error that i cannot figure out;

The error MissingReferenceException: The object of type 'RUI_ArrayButton' has been destroyed but you are still trying to access it. Your script should either check if it is null or you should not destroy the object. RUI_ArrayButton.ChangeImage (UnityEngine.Texture2D _newimage) (at Assets/Resources/RUI/Scripts/RUI_ArrayButton.cs:17) RUI_TabController.RefreshSprite () (at Assets/Resources/RUI/Scripts/RUI_TabController.cs:88) RUI_TabController.RefreshTabamount () (at Assets/Resources/RUI/Scripts/RUI_TabController.cs:137) RUI_TabEditor.TabamountEditor (.RUI_TabController _tabcontroller) (at Assets/Scripts/Editor/RUI/RUI_TabEditor.cs:65) RUI_TabEditor.OnInspectorGUI () (at Assets/Scripts/Editor/RUI/RUI_TabEditor.cs:20)

When does this happen? When i decrease the tabamount by any amount it throws this error. Other than this error everything seems to be working fine but i dont think unity throws this error for nothing.

The code thats causing this error:

     public void ChangeImage(Texture2D _newimage){
         if (ButtonImage == null) {
             Debug.Log (gameObject);
             ButtonImage = gameObject.GetComponent<RawImage> ();
         }
         ButtonImage.texture = _newimage;
         gameObject.GetComponent<RectTransform> ().sizeDelta = new Vector2 (_newimage.width, _newimage.height);
     }

Some more code (RUI_TabController class)

     public void RefreshTabamount(){
         if (Tabobjects.Length != Tabamount) {
             RefreshCheck ();
             if (Tabobjects.Length > Tabamount) {
                 int AmountToDestroy = Tabobjects.Length - Tabamount;
                 for (int i = 0; i < AmountToDestroy; i++) {
                     DestroyImmediate (Tabobjects [i]);
                 }
                 Tabobjects = gameObject.GetAllChildren ();
             }
             if (Tabobjects.Length < Tabamount) {
                 int AmountToInstantiate = Tabamount - Tabobjects.Length;
                 for (int i = 0; i < AmountToInstantiate; i++) {
                     GameObject tab = new GameObject ();
                     GameObject text = new GameObject ();
 
                     tab.transform.SetParent (gameObject.transform);
                     text.transform.SetParent (tab.transform);
 
                     tab.name = "Tab" + i;
                     text.name = "Text";
 
                     tab.AddComponent<RUI_ArrayButton> ();
                     Text tabtext = text.AddComponent<Text> ();
                     tabtext.raycastTarget = false;
 
                     RectTransform tabrect = tab.GetComponent<RectTransform> ();
                     tabrect.localScale = new Vector3 (1, 1, 1);
                     tabrect.anchorMax = new Vector2 (0, 0);
                     tabrect.anchorMin = new Vector2 (0, 0);
 
                     RectTransform textrect = text.GetComponent<RectTransform> ();
                     textrect.anchoredPosition = new Vector2 (0.0f, -0.75f);
                 }
                 Tabobjects = null;
                 Tabobjects = gameObject.GetAllChildren ();
                 RA = null;
                 RA = new RUI_ArrayButton[Tabobjects.Length];
                 for (int i = 0; i < Tabobjects.Length; i++) {
                     RA [i] = Tabobjects [i].GetComponent<RUI_ArrayButton> ();
                 }
             }
             RefreshSpacing ();
             RefreshText ();
             RefreshSprite ();
         }
     }

More code (the custom editor function that is called from the OnInspectorGUI method)

     private void TabamountEditor(RUI_TabController _tabcontroller){
         GUILayout.BeginHorizontal ();
         EditorGUILayout.LabelField ("Tabs",GUILayout.Width (60));
         EditorGUI.BeginChangeCheck();
         _tabcontroller.Tabamount = EditorGUILayout.IntSlider (_tabcontroller.Tabamount,1,100, GUILayout.Width (200));
 
         GUILayout.EndHorizontal ();
         if (EditorGUI.EndChangeCheck ()) {
             _tabcontroller.RefreshTabamount ();
         }
     }