[gitg] Field 'd_repository' should be nullable

[Ignacio Casal Quinteiro <icq src gnome org>]

commit 79dc7d1906d7e2a2fba05f8218d28b5c114cc34f
Author: Techlive Zheng <techlivezheng gmail com>
Date:   Sat Jun 1 02:45:07 2013 +0800

    Field 'd_repository' should be nullable

 plugins/history/gitg-history-navigation.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/plugins/history/gitg-history-navigation.vala b/plugins/history/gitg-history-navigation.vala
index d9086a2..059ad89 100644
--- a/plugins/history/gitg-history-navigation.vala
+++ b/plugins/history/gitg-history-navigation.vala
@@ -73,7 +73,7 @@ namespace GitgHistory
                private SList<Gtk.TreeIter?> d_parents;
                private uint d_sections;
                private Activated[] d_callbacks;
-               private Gitg.Repository d_repository;
+               private Gitg.Repository? d_repository;
 
                public signal void ref_activated(Gitg.Ref? r);