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

[Bilal Elmoussaoui <bilelmoussaoui src gnome org>]

commit 985a39d41fea94ea9f3de24b3272d0b048671e53
Author: Bilal Elmoussaoui <bil elmoussaoui gmail com>
Date:   Sat Jan 1 17:59:35 2022 +0100

    gtk: mark gtk_native_get_for_surface as nullable

 gtk/gtknative.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gtk/gtknative.c b/gtk/gtknative.c
index 8a0b74a062..0154781379 100644
--- a/gtk/gtknative.c
+++ b/gtk/gtknative.c
@@ -267,7 +267,7 @@ gtk_native_get_surface_transform (GtkNative *self,
  *
  * Finds the `GtkNative` associated with the surface.
  *
- * Returns: (transfer none): the `GtkNative` that is associated with @surface
+ * Returns: (transfer none) (nullable): the `GtkNative` that is associated with @surface
  */
 GtkNative *
 gtk_native_get_for_surface (GdkSurface *surface)