[banshee] DatabaseSource: Fix NRE in SkipTrackIfRemoved (bgo#647932)

[Gabriel Burt <gburt src gnome org>]

commit 1d372fa7635d8ad1a1640e8da5986a8325ce8642
Author: Gabriel Burt <gabriel burt gmail com>
Date:   Mon Apr 18 19:19:27 2011 -0500

    DatabaseSource: Fix NRE in SkipTrackIfRemoved (bgo#647932)

 .../Banshee.Sources/DatabaseSource.cs              |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/Core/Banshee.Services/Banshee.Sources/DatabaseSource.cs b/src/Core/Banshee.Services/Banshee.Sources/DatabaseSource.cs
index e18a9b1..785a43d 100644
--- a/src/Core/Banshee.Services/Banshee.Sources/DatabaseSource.cs
+++ b/src/Core/Banshee.Services/Banshee.Sources/DatabaseSource.cs
@@ -592,7 +592,7 @@ namespace Banshee.Sources
         protected void SkipTrackIfRemoved ()
         {
             var playback_src = ServiceManager.PlaybackController.Source as DatabaseSource;
-            if (playback_src != this && playback_src.Parent != this)
+            if (playback_src == null || (playback_src != this && playback_src.Parent != this))
                 return;
 
             var track = ServiceManager.PlayerEngine.CurrentTrack as DatabaseTrackInfo;