[gtk/bilelmoussaoui/g-i] gtk: mark gtk_flatten_list_model_get_model_for_item as nullable

[Bilal Elmoussaoui <bilelmoussaoui src gnome org>]

commit 38b8da0f5fd3a85f37ce37479c7f28fac018221e
Author: Bilal Elmoussaoui <bil elmoussaoui gmail com>
Date:   Sat Jan 1 19:07:13 2022 +0100

    gtk: mark gtk_flatten_list_model_get_model_for_item as nullable

 gtk/gtkflattenlistmodel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gtk/gtkflattenlistmodel.c b/gtk/gtkflattenlistmodel.c
index 23b26a35f4..15a164f5c9 100644
--- a/gtk/gtkflattenlistmodel.c
+++ b/gtk/gtkflattenlistmodel.c
@@ -510,7 +510,7 @@ gtk_flatten_list_model_get_model (GtkFlattenListModel *self)
  *
  * Returns the model containing the item at the given position.
  *
- * Returns: (transfer none): the model containing the item at @position
+ * Returns: (transfer none) (nullable): the model containing the item at @position
  */
 GListModel *
 gtk_flatten_list_model_get_model_for_item (GtkFlattenListModel *self,