[gtk] Fix a compiler warning

[Matthias Clasen <matthiasc src gnome org>]

commit 248c07c65e375a530551820e481ec2c6d7ff317c
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue May 7 04:01:21 2019 +0000

    Fix a compiler warning

 gtk/a11y/gtknotebookpageaccessible.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gtk/a11y/gtknotebookpageaccessible.c b/gtk/a11y/gtknotebookpageaccessible.c
index d79b603aba..1b90353029 100644
--- a/gtk/a11y/gtknotebookpageaccessible.c
+++ b/gtk/a11y/gtknotebookpageaccessible.c
@@ -261,7 +261,7 @@ gtk_notebook_page_accessible_new (GtkNotebookAccessible *notebook,
 
   atk_object_set_parent (gtk_widget_get_accessible (child), atk_object);
   nb = GTK_NOTEBOOK (gtk_accessible_get_widget (page->priv->notebook));
-  notebook_page = gtk_notebook_get_page (nb, child);
+  notebook_page = GTK_NOTEBOOK_PAGE (gtk_notebook_get_page (nb, child));
 
   g_signal_connect (notebook_page,
                     "notify::tab-label",