[gedit] notebook-stack-switcher: fix assertion at exit

[Ignacio Casal Quinteiro <icq src gnome org>]

commit f982a19e72e8b615cd19b0758e5173df38ff32e6
Author: Ignacio Casal Quinteiro <icq gnome org>
Date:   Wed Mar 25 09:45:07 2015 +0100

    notebook-stack-switcher: fix assertion at exit
    
    Fixes https://bugzilla.gnome.org/show_bug.cgi?id=746691

 gedit/gedit-notebook-stack-switcher.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)
---
diff --git a/gedit/gedit-notebook-stack-switcher.c b/gedit/gedit-notebook-stack-switcher.c
index 0575ed1..ca2b56c 100644
--- a/gedit/gedit-notebook-stack-switcher.c
+++ b/gedit/gedit-notebook-stack-switcher.c
@@ -206,7 +206,14 @@ on_notebook_switch_page (GtkNotebook                *notebook,
        GtkWidget *child;
 
        child = g_object_get_data (G_OBJECT (page), "stack-child");
-       if (child != NULL)
+
+       /* NOTE: we make the assumption here that if there is no visible child
+        * it means that the child does not contain any child already, this is
+        * to avoid an assertion when closing gedit, since the remove signal
+        * runs first on the stack handler so we try to set a visible child
+        * when the stack already does not handle that child
+        */
+       if (child != NULL && gtk_stack_get_visible_child (priv->stack) != NULL)
        {
                gtk_stack_set_visible_child (priv->stack, child);
        }