File manager is creating documents with no language for the uploaded files

When the filemanager is creating documents to hold the uploaded documents, it seems that these documents are created with no set language, even if a language is set in the wiki in the Localization area in administration.

This does not correspond to the way the folders are created (folders do get a language set), nor with another creation of document on the wiki (regular page creation process sets the language).

This is visible in the solr search, when searching for things in the wiki, the "No language" option will appear in the Languages facet, because of these documents (see attached screenshot).