[gtk+] cell-renderer: Check for NULL return in vfunc start_editing()

[Jonh Wendell <jwendell src gnome org>]

commit cc0c521c4c0d6ef5fe1c7430c97259eb11c30b85
Author: Jonh Wendell <jonh wendell intel com>
Date:   Mon Dec 16 17:31:50 2013 -0200

    cell-renderer: Check for NULL return in vfunc start_editing()
    
    This virtual function may return NULL, so, let's check if that's
    the case and exit the function apropriately.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=720554

 gtk/gtkcellrenderer.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkcellrenderer.c b/gtk/gtkcellrenderer.c
index 3ebe9ae..aa961e7 100644
--- a/gtk/gtkcellrenderer.c
+++ b/gtk/gtkcellrenderer.c
@@ -876,6 +876,9 @@ gtk_cell_renderer_start_editing (GtkCellRenderer      *cell,
                                                                (GdkRectangle *) background_area,
                                                                (GdkRectangle *) cell_area,
                                                                flags);
+  if (editable == NULL)
+    return NULL;
+
   gtk_style_context_add_class (gtk_widget_get_style_context (GTK_WIDGET (editable)),
                                GTK_STYLE_CLASS_CELL);