[blam/gtk-builder] Don't get caught by channel removals

[Carlos Martín Nieto <cmartin src gnome org>]

commit 82f47879f9bfec4b6dbf00b0d33fbc6c57c833d0
Author: Carlos Martín Nieto <cmn dwim me>
Date:   Mon Oct 7 13:30:32 2013 +0200

    Don't get caught by channel removals

 src/Blam.cs |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/Blam.cs b/src/Blam.cs
index 1ff3a8e..528ecd7 100644
--- a/src/Blam.cs
+++ b/src/Blam.cs
@@ -62,6 +62,7 @@ namespace Blam
 
                        FeedList.SelectionChanged()
                                .Select(obj => ((TreeSelection)obj.Sender).Channel())
+                               .Where(chan => chan != null)
                                .Subscribe(chan => ItemList.Channel = chan);
 
                        wireMenuItems(bld);