AddComponent giving NullReferenceException in Editor script

Having an issue using AddComponent to add a script to a newly created prefab. This is in C#. I have the script "scriptType1.js" located in my 'Assets\Scripts\' folder.

The errors I'm getting are as follow, but I have no idea what it all means. My script can't get past "AddType1Stuff()" function.

NullReferenceException: Object reference not set to an instance of an object CreatePrefabFromModels.AddType1Stuff (UnityEngine.GameObject newPrefab) (at Assets/Editor/CreatePrefabFromModels.cs:142) CreatePrefabFromModels.createNew (UnityEngine.GameObject obj, System.String localPath) (at Assets/Editor/CreatePrefabFromModels.cs:118) CreatePrefabFromModels.CreatePrefab (UnityEngine.GameObject prefab) (at Assets/Editor/CreatePrefabFromModels.cs:96) CreatePrefabFromModels.OnWizardCreate () (at Assets/Editor/CreatePrefabFromModels.cs:65) System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation. System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) UnityEditor.ScriptableWizard.OnGUI () (at C:/BuildAgent/work/6bc5f79e0a4296d6/Editor/MonoGenerated/Editor/ScriptableWizard.cs:70) System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation. System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at C:/BuildAgent/work/6bc5f79e0a4296d6/Editor/Mono/GUI/DockArea.cs:213) UnityEditor.HostView.Invoke (System.String methodName) (at C:/BuildAgent/work/6bc5f79e0a4296d6/Editor/Mono/GUI/DockArea.cs:206) UnityEditor.HostView.OnGUI () (at C:/BuildAgent/work/6bc5f79e0a4296d6/Editor/Mono/GUI/DockArea.cs:107)

CODE:

 using UnityEngine;
 using System.Collections;
 using UnityEditor;
 
 public class CreatePrefabFromModels : ScriptableWizard
 {
     
     public GameObject[] prefabsToCreate;
         
     [MenuItem ("Custom/Create Prefab from 3D Models")]
     static void CreateWizard ()
     {
         ScriptableWizard.DisplayWizard<CreatePrefabFromModels>("Create Prefab from 3D Models", "Apply");
     }
         
     void OnWizardCreate ()
     {
         foreach (GameObject prefabToCreate in prefabsToCreate)
         {
             CreatePrefab(prefabToCreate);
         }
     }
 
     static void CreatePrefab (GameObject prefab)
     {
         string localPath = "Assets/Prefabs/prefab_" + prefab.name.ToLower() + ".prefab";
         
         if (AssetDatabase.LoadAssetAtPath(localPath, typeof(GameObject)) )
         {
             if (EditorUtility.DisplayDialog("Are you sure?", "The prefab already exists. Do you want to overwrite it?", "Yes", "No"))
             {
             createNew(prefab, localPath);
             }
             else
             Debug.Log("File was not overwritten");
         }
         else
         {
             createNew(prefab, localPath);
         }            
     }
     
     
     static void createNew(GameObject obj, string localPath)
     {
         Object newPrefab = EditorUtility.CreateEmptyPrefab(localPath);    // create new empty prefab
         EditorUtility.ReplacePrefab(obj, newPrefab);                    // put the 3d model into the new prefab
         
         if (obj.name.ToLower().Contains("type1"))
         { 
             AddType1Stuff(newPrefab as GameObject);    // have to say 'as GameObject' since AddComponent won't work with an 'Object'
         }
         else if (obj.name.ToLower().Contains("type2"))
         {
             AddType2Stuff(newPrefab as GameObject);
         }
         else
         {
             Debug.Log("Object is not Type1 or Type2");
         }
         
         AssetDatabase.Refresh();
     
         GameObject clone = EditorUtility.InstantiatePrefab(newPrefab) as GameObject;
     }
     
     static void AddType1Stuff(GameObject newPrefab)
     {
         newPrefab.AddComponent<scriptType1>();
         newPrefab.AddComponent<MeshCollider>();
     }
     
     static void AddType2Stuff(GameObject newPrefab)
     {
         newPrefab.AddComponent<scriptType2>();
     }
 }