gtknotebook: Fix critical warnings on scroll events

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=604391

diff --git a/gtk/gtknotebook.c b/gtk/gtknotebook.c
index d2a987623ebb64ec553a256fd19384afeedc8626..65b7ee0c95f230cd0b32d6dbf9ec9d6d3d386d15 100644 (file)
--- a/gtk/gtknotebook.c
+++ b/gtk/gtknotebook.c
@@ -2550,7 +2550,8 @@ gtk_notebook_scroll (GtkWidget      *widget,
   for (i = 0; i < 2; i++)
     {
       if (event_widget == priv->action_widget[i] ||
-          gtk_widget_is_ancestor (event_widget, priv->action_widget[i]))
+          (priv->action_widget[i] &&
+           gtk_widget_is_ancestor (event_widget, priv->action_widget[i])))
         return FALSE;
     }