external scene object "Canvas" can not be saved in prefab asset.

今天把 scene 底下的介面給整理到 prefab 去, 結果出現這個錯誤

Reference "0" of "Panel_ThreeTiledGame" to external scene object "Canvas" can not be saved in prefab asset.
at D:\ProgramFiles(x86)\CocosCreator_2.3.3\resources\app.asar\editor\page\scene-utils\utils\prefab.js:1:3280
at n (D:\ProgramFiles(x86)\CocosCreator_2.3.3\resources\app.asar\editor\page\scene-utils\utils\prefab.js:1:2960)

後來發現是複製過來的Button Event 上面還掛著原本的 canvas 綁定, 把這個去掉在保存就好了