[gnome-contacts] App: Ensure Hdy.HeaderGroup is loaded on startup

[Niels De Graef <nielsdg src gnome org>]

commit a3fc85813317837daf1ba3778c63a32c0fbe0b08
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Wed Oct 17 14:07:39 2018 +0200

    App: Ensure Hdy.HeaderGroup is loaded on startup
    
    This is needed as we will use it in the next commit in a GtkBuilder
    descriptor.

 src/contacts-app.vala | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/src/contacts-app.vala b/src/contacts-app.vala
index 3cbded9..d577ae1 100644
--- a/src/contacts-app.vala
+++ b/src/contacts-app.vala
@@ -16,6 +16,7 @@
  */
 
 using Gtk;
+using Hdy;
 using Folks;
 
 public class Contacts.App : Gtk.Application {
@@ -320,6 +321,10 @@ public class Contacts.App : Gtk.Application {
     base.startup ();
 
     load_styling ();
+
+    // Ensure the following types are loaded on startup, which is needed for
+    // them to be instanciable by GtkBuilder.
+    typeof (HeaderGroup).ensure ();
   }
 
   public void load_styling () {