[gtk/gtk-4-6] Mark nullable arguments in GtkPaned

[Matthias Clasen <matthiasc src gnome org>]

commit c1002b20ee722aa75cd193c1c696d47631c392de
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Thu Apr 14 22:44:17 2022 +0100

    Mark nullable arguments in GtkPaned
    
    The set_start_child() and set_end_child() methods take NULL for the
    child argument, as a way to remove the child from the paned widget.

 gtk/gtkpaned.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkpaned.c b/gtk/gtkpaned.c
index ccea91f92c..bc7591a3d7 100644
--- a/gtk/gtkpaned.c
+++ b/gtk/gtkpaned.c
@@ -1571,9 +1571,11 @@ gtk_paned_new (GtkOrientation orientation)
 /**
  * gtk_paned_set_start_child: (attributes org.gtk.Method.set_property=start-child)
  * @paned: a `GtkPaned`
- * @child: the widget to add
+ * @child: (nullable): the widget to add
  *
  * Sets the start child of @paned to @child.
+ *
+ * If @child is `NULL`, the existing child will be removed.
  */
 void
 gtk_paned_set_start_child (GtkPaned *paned,
@@ -1686,9 +1688,11 @@ gtk_paned_get_shrink_start_child (GtkPaned *paned)
 /**
  * gtk_paned_set_end_child: (attributes org.gtk.Method.set_property=end-child)
  * @paned: a `GtkPaned`
- * @child: the widget to add
+ * @child: (nullable): the widget to add
  *
  * Sets the end child of @paned to @child.
+ *
+ * If @child is `NULL`, the existing child will be removed.
  */
 void
 gtk_paned_set_end_child (GtkPaned *paned,