[f-spot] Fix a crash in the loupe tool

[Stephen Shaw <sshaw src gnome org>]

commit dd4dc2c720ea9ccdd96558f8f0f45d2145d2e041
Author: Stephen Shaw <sshaw decriptor com>
Date:   Fri Feb 3 17:53:30 2012 -0700

    Fix a crash in the loupe tool
    
    Double clicking on the loupe tool caused the crash
    
    https://bugzilla.gnome.org/show_bug.cgi?id=669354

 src/Clients/MainApp/FSpot.Widgets/Loupe.cs |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/Clients/MainApp/FSpot.Widgets/Loupe.cs b/src/Clients/MainApp/FSpot.Widgets/Loupe.cs
index 1793e20..12bae67 100644
--- a/src/Clients/MainApp/FSpot.Widgets/Loupe.cs
+++ b/src/Clients/MainApp/FSpot.Widgets/Loupe.cs
@@ -520,7 +520,8 @@ namespace FSpot.Widgets {
 			};
 			ButtonPressEvent += delegate {
 				pressed = true;
-				GdkWindow.Cursor = closed_hand_cursor;
+				if (null != GdkWindow)
+					GdkWindow.Cursor = closed_hand_cursor;
 			};
 			ButtonReleaseEvent += delegate {
 				pressed = false;