[gtk+] GtkApplicationWindow: Add missing annotations

[Timm Bäder <baedert src gnome org>]

commit 5a0a870d892a149e0a065f84a9a77b6e20c05ad6
Author: Timm Bäder <mail baedert org>
Date:   Thu Oct 22 19:31:36 2015 +0200

    GtkApplicationWindow: Add missing annotations

 gtk/gtkapplicationwindow.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkapplicationwindow.c b/gtk/gtkapplicationwindow.c
index 919d92c..86739a4 100644
--- a/gtk/gtkapplicationwindow.c
+++ b/gtk/gtkapplicationwindow.c
@@ -1022,7 +1022,7 @@ gtk_application_window_set_help_overlay (GtkApplicationWindow *window,
  * Gets the #GtkShortcutsWindow that has been set up with
  * a prior call to gtk_application_window_set_help_overlay().
  *
- * Returns: the help overlay associated with @window, or %NULL
+ * Returns: (transfer none) (nullable): the help overlay associated with @window, or %NULL
  *
  * Since: 3.20
  */