Steps to reproduce

1. Use Ibexa Experience 4.6.2.
2. Add a second language in the back office.
3. Create a new content type with an address field.
4. Create a new content item of the new content type.
5. Create a translation of the content item in the new language.
6. Open the network tab in the browser.
7. Change the country in the address field.

Expected result:
No failed requests.

Actual result:
…/admin/address/form/test_type/address/pol-PL/update/78/name/ezplatform_content_forms_content_edit/country/… request fails with exception:

Warning: Undefined array key "address"
in vendor/ibexa/content-forms/src/lib/Data/Mapper/ContentUpdateMapper.php (line 45)