Custom Editors : EnumFields, Proper Use Of

Hi all, I've been experimenting with Custom Editors, and no matter how much work I put into making this script, I always get some crazy nullreference exception. :/

My question is: How can I implement an editor that shows/hides inspector variables based on the value selected from the enum box?

Here is some code I've been working on...

 [CustomEditor(typeof(ContentWindow))]
     public class ContentWindowEditor : Editor
     {
         public ContentWindow CW;
 
         void Awake()
         {
             CW = (ContentWindow)target;
         }
 
         public override void OnInspectorGUI()
         {
             serializedObject.Update();
             CW.WT = (ContentWindow.WindowType)EditorGUILayout.EnumMaskField("Window Type", CW.WT);
             serializedObject.ApplyModifiedProperties();
         }
     }

Here's the Enum

         public WindowType WT;
         public enum WindowType
         {
             ImageWindow = 0,
             TextWindow = 1,
             MiscWindow = 2
         }

This Editor script is supposed to show/hide selected Inspector elements depending on what is selected from the Enum. This is passed through a switch/case and then the relevent elements are drawn. Instead I get a NullReferenceException when loading the script or navigating to it's Inspector.

As Always, I appreciate all the help you have.

--CausticLasagne.