[iagno] Do not translate empty string

[Jiro Matsuzawa <jmatsuzawa src gnome org>]

commit d58dfe062d53a79dcafde19c8031b57973f51ff6
Author: Jiro Matsuzawa <jmatsuzawa gnome org>
Date:   Tue Mar 19 15:56:06 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=696042

 src/iagno.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/iagno.vala b/src/iagno.vala
index 725f330..43d3977 100644
--- a/src/iagno.vala
+++ b/src/iagno.vala
@@ -603,7 +603,7 @@ public class Iagno : 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));