Webspellchecker and Mathtype are not working with Vite plugin

[LukaszGudel]

Steps

1. Add Webspellchecker or Mathtype plugins to the editor build using Vite and vite-plugin-ckeditor5.
2. Start Vite dev server.

Result

The page crashes and the editor is not available. There is an error in the console:

TypeError: Cannot read properties of null (reading 'getAttribute')
    at IconView._updateXMLContent (iconview.js:67:33)
    at IconView.render (iconview.js:48:14)
    at IconView.<anonymous> (observablemixin.js:181:45)
    at IconView.fire (emittermixin.js:146:47)
    at <computed> [as render] (observablemixin.js:184:29)
    at ViewCollection._renderViewIntoCollectionParent (viewcollection.js:179:18)
    at ViewCollection.<anonymous> (viewcollection.js:63:18)
    at ViewCollection.fire (emittermixin.js:146:47)
    at ViewCollection.addMany (collection.js:106:18)
    at ViewCollection.add (collection.js:75:21)