Properties: no active row, get_cursor returns None, causing error

[Johannes Sasongko]

The track properties dialog calls gtk.TreeView.get_cursor to find the "active" row. The intention was to show this track first in the dialog, although I think that feature never got implemented.

The problem is, get_cursor can return None, and this is not handled. To reproduce:
1. Create new playlist view.
2. Drag a track to it.
3. Press the Next button, the track should start playing.
4. Tools → Track Properties.

If you don't see the error, try restarting Exaile. For some reason it doesn't happen all the time.

Traceback (most recent call last):
  File "C:\Users\js\Projects\exaile\trunk\xlgui\__init__.py", line 366, in on_track_properties
    if not pl.properties_dialog():
  File "C:\Users\js\Projects\exaile\trunk\xlgui\playlist.py", line 136, in properties_dialog
    selected = self.get_cursor()
  File "C:\Users\js\Projects\exaile\trunk\xlgui\playlist.py", line 425, in get_cursor
    track_id = self.list.get_cursor()[0][0]
TypeError: 'NoneType' object is unsubscriptable

[Johannes Sasongko (sjohannes)]

Fixed. get_cursor was returning (None, None).