[gitg] Fix check for enabling debug mode for diff

[Jesse van den Kieboom <jessevdk src gnome org>]

commit 6847eeb585eef8532035a09a4cd13bc608d37a18
Author: Jesse van den Kieboom <jesse vandenkieboom epfl ch>
Date:   Mon Oct 29 17:16:30 2012 +0100

    Fix check for enabling debug mode for diff

 libgitg-gtk/gitg-gtk-diff-view.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libgitg-gtk/gitg-gtk-diff-view.vala b/libgitg-gtk/gitg-gtk-diff-view.vala
index 3ac9203..14be23e 100644
--- a/libgitg-gtk/gitg-gtk-diff-view.vala
+++ b/libgitg-gtk/gitg-gtk-diff-view.vala
@@ -178,7 +178,7 @@ namespace GitgGtk
 
 			var settings = new WebKit.Settings();
 
-			var dbg = Environment.get_variable("GITG_GTK_DIFF_VIEW_DEBUG") != "";
+			var dbg = Environment.get_variable("GITG_GTK_DIFF_VIEW_DEBUG") != null;
 
 			if (dbg)
 			{