[gtk+] viewport: Don't destroy pixelcache while it's still used

[Benjamin Otte <otte src gnome org>]

commit e3f8316d08e211d20fb0771576d4209e763b64ab
Author: Benjamin Otte <otte redhat com>
Date:   Wed Jan 20 05:09:25 2016 +0100

    viewport: Don't destroy pixelcache while it's still used
    
    Removing the child unsets the pxielcache's style context...

 gtk/gtkviewport.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)
---
diff --git a/gtk/gtkviewport.c b/gtk/gtkviewport.c
index 3edf5ec..368374c 100644
--- a/gtk/gtkviewport.c
+++ b/gtk/gtkviewport.c
@@ -574,13 +574,11 @@ gtk_viewport_destroy (GtkWidget *widget)
   viewport_disconnect_adjustment (viewport, GTK_ORIENTATION_HORIZONTAL);
   viewport_disconnect_adjustment (viewport, GTK_ORIENTATION_VERTICAL);
 
-  if (priv->pixel_cache)
-    _gtk_pixel_cache_free (priv->pixel_cache);
-  priv->pixel_cache = NULL;
-
   g_clear_object (&priv->gadget);
 
   GTK_WIDGET_CLASS (gtk_viewport_parent_class)->destroy (widget);
+
+  g_clear_pointer (&priv->pixel_cache, _gtk_pixel_cache_free);
 }
 
 /**