Command line adding broken

Adding files and folders to playlist via command line is working incorrectly in 0.31b as well as of r2788. It only works when Exaile is not already started. Trying to add to an opened instance sometimes produces only the first line below, other times the full traceback is printed.

['/home/andy/Music/Example.ogg']
Traceback (most recent call last):
  File "/usr/local/lib/exaile/exaile.py", line 52, in <module>
    main()
  File "/usr/local/lib/exaile/exaile.py", line 49, in main
    exaile = main.Exaile()
  File "/usr/local/lib/exaile/xl/main.py", line 79, in __init__
    if xldbus.check_exit(self.options, self.args):
  File "/usr/local/lib/exaile/xl/xldbus.py", line 75, in check_exit
    iface.Enqueue(args)
  File "/usr/lib/pymodules/python2.6/dbus/proxies.py", line 140, in __call__
    **keywords)
  File "/usr/lib/pymodules/python2.6/dbus/connection.py", line 620, in call_blocking
    message, timeout)
dbus.exceptions.DBusException: org.freedesktop.DBus.Python.TypeError: Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.6/dbus/service.py", line 702, in _message_cb
    retval = candidate_method(self, *args, **keywords)
  File "/usr/local/lib/exaile/xl/xldbus.py", line 382, in Enqueue
    tracks = trax.sort_tracks([column], tracks)
  File "/usr/local/lib/exaile/xl/trax/util.py", line 79, in sort_tracks
    return sorted(trackiter, key=keyfunc, reverse=reverse)
  File "/usr/local/lib/exaile/xl/trax/util.py", line 78, in <lambda>
    artist_compilations=artist_compilations) for field in fields]
  File "/usr/local/lib/exaile/xl/trax/track.py", line 447, in get_tag_sort
    sorttag = self.__tags.get(tag + "sort")
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'