Playlist entry duplication

4bc33dbc commit caused this bug.

Steps:

• mkdir -p dir/subdir
• put a single mp3 (or any other supported file) into the dir
• put a single mp3 (or any other supported file) into the dir/subdir
• open the dir with vlc

Expected result: There should be two dirs and two files in the playlist.

Actual result: Everything is duplicated in the playlist.