[gtk+] Improve gtk_widget_insert_action_group docs

[Matthias Clasen <matthiasc src gnome org>]

commit 58e9e9d3163d32badf54e0348787f493f9109d33
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Sep 16 21:13:00 2013 -0400

    Improve gtk_widget_insert_action_group docs
    
    Mention that group can be NULL. Related to
    
    https://bugzilla.gnome.org/show_bug.cgi?id=708150

 gtk/gtkwidget.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 6ee8409..532a828 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -15520,13 +15520,16 @@ _gtk_widget_get_action_muxer (GtkWidget *widget)
  * gtk_widget_insert_action_group:
  * @widget: a #GtkWidget
  * @name: the prefix for actions in @group
- * @group: a #GActionGroup
+ * @group: (allow-none): a #GActionGroup, or %NULL
  *
  * Inserts @group into @widget. Children of @widget that implement
  * #GtkActionable can then be associated with actions in @group by
  * setting their 'action-name' to
  * @prefix.<replaceable>action-name</replaceable>.
  *
+ * If @group is %NULL, a previously inserted group for @name is removed
+ * from @widget.
+ *
  * Since: 3.6
  */
 void