[banshee] [MediaEngine] Fix recently introduced NRE (bgo#633404)

[Gabriel Burt <gburt src gnome org>]

commit 964f6719d2c6fcd687eabb6ecb1d4c1b19246ed9
Author: Gabriel Burt <gabriel burt gmail com>
Date:   Thu Oct 28 16:30:00 2010 -0500

    [MediaEngine] Fix recently introduced NRE (bgo#633404)

 .../Banshee.MediaEngine/PlayerEngine.cs            |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/Core/Banshee.Services/Banshee.MediaEngine/PlayerEngine.cs b/src/Core/Banshee.Services/Banshee.MediaEngine/PlayerEngine.cs
index 99d98ff..343f3e6 100644
--- a/src/Core/Banshee.Services/Banshee.MediaEngine/PlayerEngine.cs
+++ b/src/Core/Banshee.Services/Banshee.MediaEngine/PlayerEngine.cs
@@ -107,7 +107,7 @@ namespace Banshee.MediaEngine
             if (current_state != PlayerState.Playing) {
                 // Pre-buffering the next track only makes sense when we're currently playing
                 // Instead, just open.
-                if (track.Uri != null) {
+                if (track != null && track.Uri != null) {
                     HandleOpen (track);
                     Play ();
                 }
@@ -116,7 +116,7 @@ namespace Banshee.MediaEngine
 
             try {
                 // Setting the next track doesn't change the player state.
-                SetNextTrackUri (track.Uri);
+                SetNextTrackUri (track == null ? null : track.Uri);
             } catch (Exception e) {
                 Log.Exception ("Failed to pre-buffer next track", e);
             }