[gnome-klotski] Do not translate empty string

[John Cheetham <jcheetham src gnome org>]

commit 61894bbeb1fb6150b361b5818e4361c13086a045
Author: Jiro Matsuzawa <jmatsuzawa gnome org>
Date:   Tue Mar 19 15:48:59 2013 +0900

    Do not translate empty string
    
    Translating empty strings shows a po header entry. We must not gettext
    them.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=696038

 src/gnome-klotski.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/gnome-klotski.vala b/src/gnome-klotski.vala
index ae60459..cf7c038 100644
--- a/src/gnome-klotski.vala
+++ b/src/gnome-klotski.vala
@@ -976,7 +976,7 @@ public class Klotski : Gtk.Application
         Intl.bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
         Intl.textdomain (GETTEXT_PACKAGE);
 
-        var context = new OptionContext ("");
+        var context = new OptionContext (null);
         context.set_translation_domain (GETTEXT_PACKAGE);
         context.add_group (Gtk.get_option_group (true));