运行示例时，ckeditor-react'getAttributes'错误

Question

我正在尝试运行以下示例，以在react中创建自定义编辑器。

https://ckeditor.com/docs/ckeditor5/latest/builds/guides/integration/frameworks/react.html#using-ckeditor-5-source-2

不管我尝试什么，我总是收到以下错误：

ckeditor.js:5 TypeError: Cannot read property 'getAttribute' of null
at IconView._updateXMLContent (iconview.js:100)
at IconView.render (iconview.js:76)
at IconView.<anonymous> (observablemixin.js:254)
at IconView.fire (emittermixin.js:207)
at IconView.<computed> [as render] (observablemixin.js:258)
at ViewCollection.<anonymous> (viewcollection.js:68)
at ViewCollection.fire (emittermixin.js:207)
at ViewCollection.add (collection.js:182)
at ButtonView.render (buttonview.js:168)
at ButtonView.<anonymous> (observablemixin.js:254)