[gtk+] listbox: short-circuit if no sort function is set

[Christian Hergert <chergert src gnome org>]

commit 3724592efb87567691d47e6f02a7cfb2dc014a3d
Author: Christian Hergert <chergert redhat com>
Date:   Mon Jun 20 15:17:00 2016 -0700

    listbox: short-circuit if no sort function is set
    
    do_sort will crash if sort_func is not defined. Instead of adding a check
    there in the hot path, just check for sort_func before invalidating the
    sort of the underlying GSequence.

 gtk/gtklistbox.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtklistbox.c b/gtk/gtklistbox.c
index 91c08e3..17f1907 100644
--- a/gtk/gtklistbox.c
+++ b/gtk/gtklistbox.c
@@ -1280,6 +1280,9 @@ gtk_list_box_invalidate_sort (GtkListBox *box)
 
   g_return_if_fail (GTK_IS_LIST_BOX (box));
 
+  if (priv->sort_func == NULL)
+    return;
+
   g_sequence_sort (priv->children, (GCompareDataFunc)do_sort, box);
   g_sequence_foreach (priv->children, gtk_list_box_css_node_foreach, &previous);