Custom Editor Script Problem!!

Hi everyone I was working on Advanced AI Script.For which i had to make a Editor Script I wanted to add Array(Using List for that) of classes to the Editor Script.

So After Trying a lot i finally diceded to browse for it in Google Finall i found a soultion in (C#) but when i tried to impliment it

It seems to give Object reference not set to instace of object

Here is the script cut short

 import System.Collections.Generic;
 @CustomEditor(typeof(simpleAI))
 @UnityEngine.SerializePrivateVariables
 @CanEditMultipleObjects
 class AIEditor extends Editor{
   
 // Use this for initialization
 @SerializeField
  var AIScript:simpleAI;
 @SerializeField
 var AI_Script:SerializedObject;
 @SerializeField
 private var ShowIdlTransform:List.<boolean>;
 private var Show:boolean;

 function OnEnable(){
     
     AI_Script = new SerializedObject (target);  
     AutoMap = AI_Script.FindProperty("AutoMapWaypoints");
     
     }
   
      function OnInspectorGUI(){
      
     AIScript = target as simpleAI;
     TransformName = AIScript.gameObject.transform.name;
     super.OnInspectorGUI();
     
     serializedObject.Update();
     
     EditorGUILayout.Separator ();
     AI_Script.Update();
     
     var i:int=0;
     for(var Idl:IdleTransform in AIScript.IdleTrans){
     //for(var i:int =0;i<ShowIdlTransform.Count;i++){
     
     EditorGUILayout.Foldout(ShowIdlTransform[i],"Transform Parent Set #"+i); //<<<<<<<<<_---------------- PROBLEM HERE              
     if(ShowIdlTransform[i]){
     ShowIdlTransform[i] = 
     Idl.TheTransform = EditorGUILayout.ObjectField("The Object",Idl.TheTransform,typeof(Transform)) as Transform;
     
     Idl.ItsParent =  EditorGUILayout.ObjectField("Its Parent",Idl.ItsParent,typeof(Transform)) as Transform;
     Idl.Transisition_Anim = EditorGUILayout.ObjectField("The Transition Aniamtion",Idl.Transisition_Anim,AnimationClip);
     
     }
     i++;
     //}
     
     }
     EditorGUILayout.EndVertical();
     if(GUILayout.Button("?")){
     Show =!Show;
     }
   
     if(GUILayout.Button("Add WeaponParent Transistioner")){
     AIScript.IdleTrans.Add(new IdleTransform());
     ShowIdlTransform.Add(true);
     }
     }
     
     AI_Script.ApplyModifiedProperties();
     }
     }

Here IdleTransform is a class

 simple AI
 
 var IdleTrans:List.<IdleTransform>;
 @System.Serializable
 class IdleTransform{
 var Transisition_Anim:AnimationClip;
 var TheTransform:Transform;
 var ItsParent:Transform;
 }

-------------------------------## Solution ##-----------------

Edit

Hi all i figured out the solution the problem was unity was resetiing the list of ShowIdlTransform[i]

The solution was to Add this line

 function Enable(){
         ShowIdlTransform=new List.<boolean>(new boolean[AIScript.IdleTrans.Count]);
         }

and

Alter this

     for(var i:int =0;i < AIScript.IdleTrans.Count;i++){
      ShowIdlTransform[i] =  EditorGUILayout.Foldout(ShowIdlTransform[i],"Transform Parent Set #"+i); 
 if( ShowIdlTransform[i]){
 Idl.TheTransform = EditorGUILayout.ObjectField("The Object",Idl.TheTransform,typeof(Transform)) as Transform;
     
     Idl.ItsParent =  EditorGUILayout.ObjectField("Its Parent",Idl.ItsParent,typeof(Transform)) as Transform;
 }
     }