When Content is sent to Trash, Contents with Translations that link to it inside RichText field will break and Editors won't be able to Edit them.

Steps to reproduce
1. Clean installation of eZ Platform 2.5.6
2. Sign in to the BackOffice as admin User.
3. Add a Second Language: German|ger-DE.
4. In Home create a new Article Some Article. Publish it.
5. In Home create a new Article Test Article Eng in English language. In "Body" field create a link pointing to Some Article. Publish it.
6. Create a new German Translation Test Article Ger for Test Article English. In "Body" field create a link pointing to Some Article. Publish it.
7. Send Some Article to Trash.
8a. Go to Test Article Eng, press the "Edit" button, choose the English language.
8b. Go to Test Article Eng, press the "Edit" button, choose the German language. From Dialog create a new draft. In "Body" Field remove the link (with "unlink" button). Press "Publish" button.

*Result - a"
The page will be refreshed with "Content fields did not validate" error.

*Result - b"
Publish will fail with 500 exception "Content fields did not validate".