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();
        }
    }
}

If you use Editor.CreateCachedEditor method while creating your ‘static’ editor instance (instead of Editor.CreateEditor for a non-static editor), these exceptions disappear, also use DestroyImmediate at OnDisable for your static editor.