still return a valid track even when no extractors support it

that is the case when we get an audio file not with a format not yet
supported by KFileMetaData

BUG: 433892
FIXED-IN: 21.04
1 job for release/20.12 in 25 seconds (queued for 39 minutes and 20 seconds)
latest
Status Job ID Name Coverage
  Build
passed #95154
reuse

00:00:25