submodule bug fix & Clip extend

移除submodule重复引用的问题，
Clip现在可以保存任意GameElement，且任意指定物体作为父物体加载

Assets/Scripts/DynamicUI/DynamicUIElements/Simple/DynamicUIButton.cs

@@ -18,11 +18,14 @@ namespace Ichni.Editor
             this.buttonText.text = buttonText;
             if(!hasTitle) title.gameObject.SetActive(false);
         }
-        
+
         public void ApplyFunction(UnityAction function)
         {
             button.onClick.AddListener(function);
-            button.onClick.AddListener(connectedBaseElement.Refresh);
+            if (connectedBaseElement != null)
+            {
+                button.onClick.AddListener(connectedBaseElement.Refresh);
+            }
         }
     }
 }