TYPO3 Core

Steps to reproduce:

1. Create a site with at least two language
2. Create a page within the site
3. Create a content element in default language (don't save yet)
4. Switch language of content element to all languages (-1) (don't save yet)
5. Attach a file relation and save.

Result:
The relation will be saved with 0 for languages, which can be confirmed by select sys_language_uid from sys_file_reference once saved.

Expected:
The relation will be saved with -1 for language, as that's what was chosen in the parent while creating the relation.