Pre-filled Playlist field

Hello,
I did a small patch on the PlaylistFilesController which stores the last loaded playlist and prefills this value in the "Save Playlist as" textfield. If since application start no playlist was loaded, it will fill an empty string.
I'd be glad if you can pull that little convenience. Please note I'm not an experienced Cocoa developer and feel free to give me feedback about bad code.
best regards
Lukas