[gtk+/gtk-3-22] Window: Document get_icon() return as nullable

[Daniel Boles <dboles src gnome org>]

commit e09c1031879a5734a82a433fbcbb5aeddb7bdbf3
Author: Daniel Boles <dboles src gnome org>
Date:   Thu Nov 9 09:44:49 2017 +0000

    Window: Document get_icon() return as nullable

 gtk/gtkwindow.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkwindow.c b/gtk/gtkwindow.c
index bbbb9ee..4143c3a 100644
--- a/gtk/gtkwindow.c
+++ b/gtk/gtkwindow.c
@@ -4859,7 +4859,7 @@ gtk_window_get_icon_name (GtkWindow *window)
  * called gtk_window_set_icon_list(), gets the first icon in
  * the icon list).
  *
- * Returns: (transfer none): icon for window
+ * Returns: (transfer none) (nullable): icon for window or %NULL if none
  **/
 GdkPixbuf*
 gtk_window_get_icon (GtkWindow  *window)