[gtk/bilelmoussaoui/g-i] gtk: mark MenuButton::get_label/get_icon_name as nullable

[Bilal Elmoussaoui <bilelmoussaoui src gnome org>]

commit 1d72024605e31e3ed264a63c9428f84455685bb0
Author: Bilal Elmoussaoui <bil elmoussaoui gmail com>
Date:   Sat Jan 1 18:38:56 2022 +0100

    gtk: mark MenuButton::get_label/get_icon_name as nullable

 gtk/gtkmenubutton.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkmenubutton.c b/gtk/gtkmenubutton.c
index 370956da85..67c3236508 100644
--- a/gtk/gtkmenubutton.c
+++ b/gtk/gtkmenubutton.c
@@ -1059,7 +1059,7 @@ gtk_menu_button_set_icon_name (GtkMenuButton *menu_button,
  *
  * Gets the name of the icon shown in the button.
  *
- * Returns: the name of the icon shown in the button
+ * Returns: (nullable): the name of the icon shown in the button
  */
 const char *
 gtk_menu_button_get_icon_name (GtkMenuButton *menu_button)
@@ -1182,7 +1182,7 @@ gtk_menu_button_set_label (GtkMenuButton *menu_button,
  *
  * Gets the label shown in the button
  *
- * Returns: the label shown in the button
+ * Returns: (nullable): the label shown in the button
  */
 const char *
 gtk_menu_button_get_label (GtkMenuButton *menu_button)