Referenced node changes language if different from node with IEF complex form

[4hardfire]

https://www.drupal.org/project/inline_entity_form/issues/2908530

[rutiolma]

The patch is really simple but there is no feedback and no tests. Since it changes behavior, I guess it is better to postpone it until there are new developments.

To mitigate the issue:

• all related content should be translated before relating it to the target language.
• don't use a language selector on entity relationship popup window and allow only "current language" relationships.