[mistelix] Fixes compilation with old Mono.Cairo libraries

[Jordi Mas <jmas src gnome org>]

commit 34b90f7419146016fc789875f4513d7ff5d16722
Author: Jordi Mas <jmas softcatala org>
Date:   Fri Jul 17 18:50:37 2009 +0200

    Fixes compilation with old Mono.Cairo libraries

 src/dialogs/ThemeSelectionDialog.cs |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/dialogs/ThemeSelectionDialog.cs b/src/dialogs/ThemeSelectionDialog.cs
index a301238..57d0335 100644
--- a/src/dialogs/ThemeSelectionDialog.cs
+++ b/src/dialogs/ThemeSelectionDialog.cs
@@ -161,7 +161,7 @@ namespace Mistelix.Dialogs
 				if (cached_image == false) {
 
 					if (image != null)
-						image.Dispose ();
+						((IDisposable)image).Dispose ();
 
 					image = new Cairo.ImageSurface (Cairo.Format.ARGB32, project.Details.Width, project.Details.Height);
 					Cairo.Context chight = new Cairo.Context (image);