[gtk+/gtk-3-16] notebook: Fix assert in ::drag-motion

[Emmanuele Bassi <ebassi src gnome org>]

commit 873cc0e352576a6a0a9d78d49d1575b6f92453cf
Author: Carlos Garnacho <carlosg gnome org>
Date:   Tue May 26 16:26:59 2015 +0200

    notebook: Fix assert in ::drag-motion
    
    The drag destination might be empty, we shouldn't be checking whether
    it contains pages at all. Instead, check the source notebook, which
    ought to have a selected page if you're dragging something from there.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=749893

 gtk/gtknotebook.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtknotebook.c b/gtk/gtknotebook.c
index ef27191..9edb66c 100644
--- a/gtk/gtknotebook.c
+++ b/gtk/gtknotebook.c
@@ -3829,8 +3829,6 @@ gtk_notebook_drag_motion (GtkWidget      *widget,
       goto out;
     }
 
-  g_assert (priv->cur_page != NULL);
-
   stop_scrolling (notebook);
   target = gtk_drag_dest_find_target (widget, context, NULL);
   tab_target = gdk_atom_intern_static_string ("GTK_NOTEBOOK_TAB");
@@ -3844,6 +3842,7 @@ gtk_notebook_drag_motion (GtkWidget      *widget,
       retval = TRUE;
 
       source = GTK_NOTEBOOK (gtk_drag_get_source_widget (context));
+      g_assert (source->priv->cur_page != NULL);
       source_child = source->priv->cur_page->child;
 
       group = notebook->priv->group;