[gtk+] Expander: get_label() return is nullable

[Daniel Boles <dboles src gnome org>]

commit 7161b57063d56a01bd7fb127c1ee1109add98cb7
Author: Daniel Boles <dboles src gnome org>
Date:   Fri Sep 15 18:24:24 2017 +0100

    Expander: get_label() return is nullable
    
    Also, use gchar to match the header.

 gtk/gtkexpander.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkexpander.c b/gtk/gtkexpander.c
index 6e9b430..1262363 100644
--- a/gtk/gtkexpander.c
+++ b/gtk/gtkexpander.c
@@ -1120,12 +1120,12 @@ gtk_expander_set_label (GtkExpander *expander,
  * be avoided by fetching the label text directly from the label
  * widget.
  *
- * Returns: The text of the label widget. This string is owned
+ * Returns: (nullable): The text of the label widget. This string is owned
  *     by the widget and must not be modified or freed.
  *
  * Since: 2.4
  */
-const char *
+const gchar *
 gtk_expander_get_label (GtkExpander *expander)
 {
   GtkExpanderPrivate *priv;