[gtk/arnaudb/annotate-set-title] Add "allow-none" annotation.

[Arnaud B. <arnaudb src gnome org>]

commit 8b7e002c0dbf5a26b1af87fa7e2236564d5d395f
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Fri Nov 27 15:57:55 2020 +0100

    Add "allow-none" annotation.

 gtk/gtkwindow.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkwindow.c b/gtk/gtkwindow.c
index fe0e3fdf83..719fbc09bb 100644
--- a/gtk/gtkwindow.c
+++ b/gtk/gtkwindow.c
@@ -1937,7 +1937,7 @@ gtk_window_new (void)
 /**
  * gtk_window_set_title:
  * @window: a #GtkWindow
- * @title: title of the window
+ * @title: (allow-none): title of the window, or %NULL
  * 
  * Sets the title of the #GtkWindow. The title of a window will be
  * displayed in its title bar; on the X Window System, the title bar
@@ -1950,7 +1950,7 @@ gtk_window_new (void)
  * 
  **/
 void
-gtk_window_set_title (GtkWindow   *window,
+gtk_window_set_title (GtkWindow  *window,
                       const char *title)
 {
   GtkWindowPrivate *priv = gtk_window_get_instance_private (window);