[banshee] GStreamerSharp: Fix crash when ripping to non-MP3 formats

[Bertrand Lorentz <blorentz src gnome org>]

commit 61f8eb71bf4e982495b49df28fc3b1eaf73b0d0a
Author: Bertrand Lorentz <bertrand lorentz gmail com>
Date:   Sun Jan 5 16:01:00 2014 +0100

    GStreamerSharp: Fix crash when ripping to non-MP3 formats
    
    Only get the value of the "mpegversion" field is we're dealing with an
    MPEG file. This prevents an NRE because that field is not present.

 .../Banshee.GStreamerSharp/AudioCdRipper.cs        |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)
---
diff --git a/src/Backends/Banshee.GStreamerSharp/Banshee.GStreamerSharp/AudioCdRipper.cs 
b/src/Backends/Banshee.GStreamerSharp/Banshee.GStreamerSharp/AudioCdRipper.cs
index ea4c222..47be850 100644
--- a/src/Backends/Banshee.GStreamerSharp/Banshee.GStreamerSharp/AudioCdRipper.cs
+++ b/src/Backends/Banshee.GStreamerSharp/Banshee.GStreamerSharp/AudioCdRipper.cs
@@ -313,10 +313,9 @@ namespace Banshee.GStreamerSharp
                         string mimetype = str.Name;
                         int mpeg_layer;
 
-                        GLib.Value val = str.GetValue ("mpegversion");
-
                         // Prefer and adjust audio/mpeg, leaving MP3 as audio/mpeg
                         if (mimetype.StartsWith ("audio/mpeg")) {
+                            GLib.Value val = str.GetValue ("mpegversion");
                             mpeg_layer = (Int32)val.Val;
                             switch (mpeg_layer) {
                                 case 2: mimetype = "audio/mp2"; break;