Recttransform CustomEditor extension

Hi,

Since Text component can't be easily extended I decided to add a Button to Recttransform instead. The script works fine for a while, but sometimes it floods with Debug errors :

 NullReferenceException: (null)
 UnityEditor.SerializedObject..ctor (UnityEngine.Object[] objs, UnityEngine.Object context) (at C:/buildslave/unity/build/artifacts/generated/common/editor/SerializedPropertyBindings.gen.cs:87)
 UnityEditor.Editor.GetSerializedObjectInternal () (at C:/buildslave/unity/build/artifacts/generated/common/editor/EditorBindings.gen.cs:193)
 UnityEditor.Editor.get_serializedObject () (at C:/buildslave/unity/build/artifacts/generated/common/editor/EditorBindings.gen.cs:185)
 UnityEditor.RectTransformEditor.OnEnable () (at C:/buildslave/unity/build/Editor/Mono/Inspector/RectTransformEditor.cs:100)

Restarting Unity solves the problem, but maybe someone can point me out what could be wrong with this script :

 namespace Editor
 {
     using System.Reflection;
     using UnityEditor;
     using UnityEngine;
     using UnityEngine.UI;
 
     [CustomEditor(typeof(RectTransform))]
     public class RectTransformTest : Editor
     {
         private Editor editorInstance;
 
         private void OnEnable()
         {
             var assembly = Assembly.GetAssembly(typeof(Editor));
             if (assembly == null) return;
             var rtEditor = assembly.GetType("UnityEditor.RectTransformEditor");
             if (rtEditor == null) return;
             if (target   != null) editorInstance = CreateEditor(target, rtEditor);
         }
 
         public override void OnInspectorGUI()
         {
             if (editorInstance != null) editorInstance.OnInspectorGUI();
             if (target         == null) return;
 
             var t = target as RectTransform;
             if (t == null || !t.GetComponent<Text>()) return;
             if (!GUILayout.Button("Color Uppercase")) return;
             Color color;
             t.GetComponent<Text>().text = t.GetComponent<Text>().text.ColorUppercase("FFFFFF");
 
             if (ColorUtility.TryParseHtmlString("#FFA300FF", out color))
             {
                 t.GetComponent<Text>().color = color;
             }
 
             if (t.GetComponent<Outline>() == null) t.gameObject.AddComponent<Outline>();
             SceneView.RepaintAll();
         }
     }
 }