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

[Bilal Elmoussaoui <bilelmoussaoui src gnome org>]

commit d58b7fa779c2d185529ebb7a9c5c5fa6ca907381
Author: Bilal Elmoussaoui <bil elmoussaoui gmail com>
Date:   Sat Jan 1 18:19:41 2022 +0100

    gtk: mark gtk_text_mark_get_buffer as nullable

 gtk/gtktextmark.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gtk/gtktextmark.c b/gtk/gtktextmark.c
index 878c6ed57f..58b56057c2 100644
--- a/gtk/gtktextmark.c
+++ b/gtk/gtktextmark.c
@@ -346,7 +346,7 @@ gtk_text_mark_get_deleted (GtkTextMark *mark)
  *
  * Returns %NULL if the mark is deleted.
  *
- * Returns: (transfer none): the mark’s `GtkTextBuffer`
+ * Returns: (transfer none) (nullable): the mark’s `GtkTextBuffer`
  */
 GtkTextBuffer*
 gtk_text_mark_get_buffer (GtkTextMark *mark)