[hyena/gtk3] ListView: null check before subscribing to ValueChanged (bgo#706272)

[Andrés Aragoneses <aaragoneses src gnome org>]

commit 3d31127ee30fa3b988c243cb4bf367d348e8e548
Author: Andrés G. Aragoneses <knocte gmail com>
Date:   Sat Aug 24 12:08:32 2013 +0200

    ListView: null check before subscribing to ValueChanged (bgo#706272)
    
    This was causing a NullReferenceException when closing the listview
    window when running the demo ('make hg').

 .../ListView/ListView_Interaction.cs               |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/Hyena.Gui/Hyena.Data.Gui/ListView/ListView_Interaction.cs 
b/Hyena.Gui/Hyena.Data.Gui/ListView/ListView_Interaction.cs
index cc7ecb3..4c533a5 100644
--- a/Hyena.Gui/Hyena.Data.Gui/ListView/ListView_Interaction.cs
+++ b/Hyena.Gui/Hyena.Data.Gui/ListView/ListView_Interaction.cs
@@ -86,7 +86,9 @@ namespace Hyena.Data.Gui
                     vadjustment.ValueChanged -= OnVadjustmentChanged;
                 }
                 vadjustment = value;
-                vadjustment.ValueChanged += OnVadjustmentChanged;
+                if (vadjustment != null) {
+                    vadjustment.ValueChanged += OnVadjustmentChanged;
+                }
                 UpdateAdjustments ();
             }
         }
@@ -102,7 +104,9 @@ namespace Hyena.Data.Gui
                     hadjustment.ValueChanged -= OnHadjustmentChanged;
                 }
                 hadjustment = value;
-                hadjustment.ValueChanged += OnHadjustmentChanged;
+                if (hadjustment != null) {
+                    hadjustment.ValueChanged += OnHadjustmentChanged;
+                }
                 UpdateAdjustments ();
             }
         }