Steps to reproduce:

• Create a page with default language english.
• Add a container (e.g. "Two column content") with a "Regular Text Element" inside it.
• Translate the page to german.
• Use the translation wizard to translate container and text element to german.
• Edit the translated (german) text element.
• In the tab "Language" change the language to English and save.

Actual result

The text element disappears and is now listed on the english page as "Unused element".
In the database, it still has the tx_container_parent reference to the german container element.

Expected result

When changing the language of an element inside a container, the container reference should be changed too or set to zero.
The element should not become an "Unused element".