SoundSource - Fixing TString convertion
- Try converting a TString from a metadata directly to QString can produce segfaults.
- We must check if it is valid before convert it.
Merge branch 'coverArtSupport' of https://github.com/cardinot/mixxx into coverArtSupport_2
Merge branch 'coverArtSupport_2' of https://github.com/cardinot/mixxx into coverArtSupport_3