[gnome-music] player: don't crash when selecting a random iter and playlist is empty

[Vadim Rutkovsky <vrutkovsky src gnome org>]

commit 6b0aa555b36962b0aebaa3ddff8252678749e691
Author: Vadim Rutkovsky <vrutkovs redhat com>
Date:   Wed Aug 26 15:27:01 2015 +0200

    player: don't crash when selecting a random iter and playlist is empty

 gnomemusic/player.py |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/gnomemusic/player.py b/gnomemusic/player.py
index caca45a..82b1680 100644
--- a/gnomemusic/player.py
+++ b/gnomemusic/player.py
@@ -406,6 +406,8 @@ class Player(GObject.GObject):
         first_iter = self.playlist.get_iter_first()
         if not currentTrack:
             currentTrack = first_iter
+        if not currentTrack:
+            return None
         if hasattr(self.playlist, "iter_is_valid") and\
            not self.playlist.iter_is_valid(currentTrack):
             return None