[gitg] Protect against head_name being null

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

commit 02b6bb0681dd58424daeadd6a4b8e2fdbc7b3ed3
Author: Jesse van den Kieboom <jessevdk gnome org>
Date:   Wed Aug 5 22:09:15 2015 +0200

    Protect against head_name being null

 gitg/gitg-window.vala |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)
---
diff --git a/gitg/gitg-window.vala b/gitg/gitg-window.vala
index ed4dfb0..180f8df 100644
--- a/gitg/gitg-window.vala
+++ b/gitg/gitg-window.vala
@@ -373,7 +373,14 @@ public class Window : Gtk.ApplicationWindow, GitgExt.Application, Initable
                        }
                        catch {}
 
-                       d_header_bar.set_subtitle(Markup.escape_text(head_name));
+                       if (head_name != null)
+                       {
+                               d_header_bar.set_subtitle(Markup.escape_text(head_name));
+                       }
+                       else
+                       {
+                               d_header_bar.set_subtitle(null);
+                       }
                }
                else
                {