Preconditions: existing content type with richtext
1. Create two Content Items with richtext: item1 and item2
2. Embed item2 in item1
3. Click Publish
4. Send item2 to trash
5. Go to edit mode of item1 there is small, grey square in richtext - see attachment. Maybe it should be removed completely.
There is also an error message displayed: Cannot read property 'value' of undefined

Update: in v1 there is nice information for a user - see attachment.