[banshee] ThickClient: prever ANE over NRE

[AndrÃs Aragoneses <aaragoneses src gnome org>]

commit 4dc7c3a625d2216dc358d2c82926869c8b724a9f
Author: Andres G. Aragoneses <knocte gmail com>
Date:   Wed Jan 18 23:19:10 2012 +0000

    ThickClient: prever ANE over NRE
    
    A user has managed to reproduce a NRE which
    has a stacktrace that leads me to think that
    the 'model' argument was null, so throw an
    ArgumentNullException to be sure and get
    better debugging info next time. (Will help
    bgo#667625 if it appears again.)
    
    Signed-off-by: Alexander Kojevnikov <alexk gnome org>

 .../Banshee.Sources.Gui/SourceView.cs              |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/src/Core/Banshee.ThickClient/Banshee.Sources.Gui/SourceView.cs b/src/Core/Banshee.ThickClient/Banshee.Sources.Gui/SourceView.cs
index a91d056..1401fa6 100644
--- a/src/Core/Banshee.ThickClient/Banshee.Sources.Gui/SourceView.cs
+++ b/src/Core/Banshee.ThickClient/Banshee.Sources.Gui/SourceView.cs
@@ -130,6 +130,10 @@ namespace Banshee.Sources.Gui
 
             source_column.PackStart (header_renderer, true);
             source_column.SetCellDataFunc (header_renderer, new Gtk.CellLayoutDataFunc ((layout, cell, model, iter) => {
+                if (model == null) {
+                    throw new ArgumentNullException ("model");
+                }
+
                 var type = (SourceModel.EntryType) model.GetValue (iter, (int)SourceModel.Columns.Type);
                 header_renderer.Visible = type == SourceModel.EntryType.Group;
                 source_renderer.Visible = type == SourceModel.EntryType.Source;