Element in the block quote doesn't remove if selection contains three block elements

[Mgsy]

🐞 Is this a bug report or feature request? (choose one)

• Bug report

💻 Version of CKEditor

1.0.0-alpha2

📋 Steps to reproduce

1. Go to http://localhost:8125/ckeditor5-core/tests/manual/article.html.
2. Start the selection in the first block quote's paragraph and move it to the OL List item 2.
3. Press delete.

✅ Expected result

Paragraph, image and list item have been removed.

❎ Actual result

Only image and list item have been removed.

📃 Other details that might be useful

GIF

Notes
If you try to put the selection in the paragraph which should be deleted, you'll get the notification in the console:

model-selection-range-in-graveyard: Trying to add a Range that is in the graveyard root. Range rejected. Read more: https://ckeditor5.github.io/docs/nightly/ckeditor5/latest/framework/guides/support/error-codes.html#model-selection-range-in-graveyard
 undefined

If you try to make undo, the paragraph will be restored.

This bug is reproducible only if the selection contains at least one block from the block quote and two blocks from outside the block quote.

I'm not able to reproduce it in https://ckeditor5.github.io/, so it might be a regression

Other information
OS: Windows 10, MacOS X
Browser: All browsers

[Reinmar]

It's indeed some kind of a regression. Looks like a differ, but I'm not sure whether on 19 Dec we had a differ already.

cc @scofalik

[scofalik]

Yes, I found what causes the bug and it is indeed a bug in differ. I am on it.

[scofalik]

Will be fixed by ckeditor/ckeditor5-engine#1316