Steps to reproduce:

1. Create content A
2. *Create content *B, which has RichtText fields
3. Embed content A in RichtText field of the content B
4. Remove content A
5. *Try to edit content *B

Expected result: you would be able to edit the content

Actual result: "Cannot read property 'value' of undefined" error is shown. And if you have a lot of content in the RichText field, it is hard to understand where this error comes from.