[gnome-music] player: don't check iter for validness if model can't do that

[Vadim Rutkovsky <vrutkovsky src gnome org>]

commit 02647f22d807a5ddf6071da8926c8d5125515dad
Author: Vadim Rutkovsky <vrutkovs redhat com>
Date:   Wed Jun 17 11:23:27 2015 +0200

    player: don't check iter for validness if model can't do that
    
    Fixes https://bugzilla.gnome.org/show_bug.cgi?id=749307

 gnomemusic/player.py |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/gnomemusic/player.py b/gnomemusic/player.py
index f56ed5c..6a9f63e 100644
--- a/gnomemusic/player.py
+++ b/gnomemusic/player.py
@@ -371,7 +371,10 @@ class Player(GObject.GObject):
 
     @log
     def _get_random_iter(self, currentTrack):
-        if not currentTrack or not self.playlist.iter_is_valid(currentTrack):
+        if not currentTrack:
+            return None
+        if hasattr(self.playlist, "iter_is_valid") and\
+           not self.playlist.iter_is_valid(currentTrack):
             return None
         currentPath = int(self.playlist.get_path(currentTrack).to_string())
         rows = self.playlist.iter_n_children(None)