[gnome-boxes] properties: Make buttons vertically centered

[Zeeshan Ali Khattak <zeeshanak src gnome org>]

commit 2e40deea1242d63440e2bee73fcb80aad454bd67
Author: Yosef Or Boczko <yoseforb gmail com>
Date:   Mon Sep 2 20:50:20 2013 +0300

    properties: Make buttons vertically centered
    
    https://bugzilla.gnome.org/show_bug.cgi?id=707296

 src/properties.vala |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/properties.vala b/src/properties.vala
index e1b7aa5..43f300e 100644
--- a/src/properties.vala
+++ b/src/properties.vala
@@ -228,6 +228,7 @@ private class Boxes.Properties: Boxes.UI {
         var back_image = new Gtk.Image.from_icon_name (back_icon, Gtk.IconSize.MENU);
         back = new Gtk.Button ();
         back.set_image (back_image);
+        back.valign = Gtk.Align.CENTER;
         back.get_style_context ().add_class ("image-button");
         toolbar.pack_start (back);
         back.clicked.connect ((button) => { App.app.ui_state = App.app.previous_ui_state; });