Disabled language is still available when editing item.

Steps:

1. Add another language to the back-office.
2. Create e.g. an article in base language.
3. Add a translation to this article.
4. Disable the second language in the back-office.
5. Edit the article.
6. Choose second language.

Actual result: Edit form is not opened, warning is displayed This value is not valid..
Expected result: Second language is not available when editing.