Occasionally error when Move range between different roots.

[misterPeng]

📝 Provide detailed reproduction steps (if any)

1. On MultirootEditor.I listened to the view render event to determine if the height of the dom of root where the selection is located exceeds maxHeight. If so, then root exceeds maxHeight's range move to nextRoot.mul-editor.zip is my code.
2. Enter a lot of content, so that it can hold more than 3 roots.
3. Enter the content in the first root, triggering the operation described in the first point.There will be an accidental bug.

✔️ Expected result

The operation described in the first point is no bug.

❌ Actual result

remove.js?802d:17 Uncaught TypeError: Cannot read property 'parentNode' of undefined

at remove (remove.js?802d:17)
at Renderer._updateChildren (renderer.js?fb19:571)
at Renderer.render (renderer.js?fb19:203)
at View._render (view.js?4b17:676)
at View.eval (view.js?4b17:187)
at View.fire (emittermixin.js?da0d:207)
at View.change (view.js?4b17:478)
at View._disableRendering (view.js?4b17:663)
at Model.EditingController.listenTo.priority (editingcontroller.js?d38d:82)
at Model.fire (emittermixin.js?da0d:207)`

at Renderer._updateChildren (renderer.js?fb19:571), the i == actualDomChildren.length.Is it caused by my code, because the api call error?

📃 Other details

mul-editor.zip

• Browser: chrome 77.0.3865.120
• CKEditor version: 12.4.0

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[Reinmar]

It seems that it's related to couple other issues that we've seen. Closing for now as DUP of #6092.