[gnome-photos] preview-view: Unref the PreviewNavButtons during destruction

[Debarshi Ray <debarshir src gnome org>]

commit 8aa2acdd1ee718e2304eb49b5a3ce6e16c3963be
Author: Debarshi Ray <debarshir gnome org>
Date:   Mon Dec 14 18:34:37 2015 +0100

    preview-view: Unref the PreviewNavButtons during destruction

 src/photos-preview-view.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/photos-preview-view.c b/src/photos-preview-view.c
index f950418..9e81c4d 100644
--- a/src/photos-preview-view.c
+++ b/src/photos-preview-view.c
@@ -511,6 +511,7 @@ photos_preview_view_dispose (GObject *object)
   g_clear_object (&priv->node);
   g_clear_object (&priv->item_mngr);
   g_clear_object (&priv->mode_cntrlr);
+  g_clear_object (&priv->nav_buttons);
 
   G_OBJECT_CLASS (photos_preview_view_parent_class)->dispose (object);
 }