#623 Playlist: not consecutive file adding in all cases

[goetz]

With the "Add consecutive files" option enabled, when opening a file (part of a folder with many other files with the same name pattern, in a acceding order), it isn't added with the rest of the files in a consecutively in the playlist.

For example, when opening "File1 - 01.ext":

Instead of:
File1 - 01.ext
File1 - 02.ext
File1 - 03.ext
File2 - 01.ext
File2 - 02.ext
File2 - 03.ext
File3 - 01.ext
File3 - 02.ext
File3 - 03.ext

It becomes:
File1 - 01.ext
File2 - 01.ext
File3 - 01.ext

in the paylist.