[swell-foop] Do not translate empty string

[Jiro Matsuzawa <jmatsuzawa src gnome org>]

commit 3398dddaaecc01fd70b69c5d2f9749ada19a38b7
Author: Jiro Matsuzawa <jmatsuzawa gnome org>
Date:   Tue Mar 19 15:59:59 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=696044

 src/swell-foop.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/swell-foop.vala b/src/swell-foop.vala
index 8e15d1c..6d665b2 100644
--- a/src/swell-foop.vala
+++ b/src/swell-foop.vala
@@ -432,7 +432,7 @@ public class SwellFoop : Gtk.Application
             return Posix.EXIT_FAILURE;
         }
 
-        var context = new OptionContext ("");
+        var context = new OptionContext (null);
         context.set_translation_domain (GETTEXT_PACKAGE);
 
         context.add_group (Gtk.get_option_group (true));