Fixed resource leak when updating Expression preview

Assets/VRM10/Editor/Components/Expression/VRM10ExpressionEditor.cs

@@ -60,23 +60,36 @@ namespace UniVRM10
             {
                 return;
             }
-            ClearScene();
+            ClearPreview();
             m_target.Prefab = prefab;
+            Initialize();
         }
 
         void OnEnable()
+        {
+            Initialize();
+        }
+
+        void OnDisable()
+        {
+            ClearPreview();
+        }
+
+        void Initialize()
         {
             m_target = (VRM10Expression)target;
             m_renderer = new PreviewFaceRenderer();
         }
 
-        void OnDisable()
+        void ClearPreview()
         {
             if (m_renderer != null)
             {
                 m_renderer.Dispose();
                 m_renderer = null;
             }
+
+            m_serializedEditor = null;
             ClearScene();
         }