File extension is 'None' when downloading a track

Steps to reproduce

1. Visit a track file page.
2. Click on Download (Télécharger)

What happens?

Download dialog presents a file with the right name except for the extension, which is set to 'None'.

What is expected?

What is expeted is .flac, or .ogg, or .mp3, depending of the original file extension.

Context

Running latest version of FW.