[banshee] GStreamerSharp: prevent potential NRE in FindOverlay()

[Andrés Aragoneses <aaragoneses src gnome org>]

commit f40d482b13ab2e74635db8e77501380e3e715521
Author: Andrés G. Aragoneses <knocte gmail com>
Date:   Wed Oct 30 15:46:58 2013 +0100

    GStreamerSharp: prevent potential NRE in FindOverlay()

 .../Banshee.GStreamerSharp/VideoManager.cs         |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/Backends/Banshee.GStreamerSharp/Banshee.GStreamerSharp/VideoManager.cs 
b/src/Backends/Banshee.GStreamerSharp/Banshee.GStreamerSharp/VideoManager.cs
index 0e55bad..c5e2bdb 100644
--- a/src/Backends/Banshee.GStreamerSharp/Banshee.GStreamerSharp/VideoManager.cs
+++ b/src/Backends/Banshee.GStreamerSharp/Banshee.GStreamerSharp/VideoManager.cs
@@ -159,6 +159,9 @@ namespace Banshee.GStreamerSharp
                     ? ((Bin)video_sink).GetByInterface (new XOverlayAdapter ().GType)
                     : video_sink;
 
+                if (xoverlay_element == null) {
+                    return false;
+                }
                 xoverlay = new XOverlayAdapter (xoverlay_element.Handle);
 
                 if (!PlatformDetection.IsWindows) {