[libadwaita] AdwApplication: Fix memory leak in update_stylesheet

[Alexander Mikhaylenko <alexm src gnome org>]

commit fcf62885bb28ec1da95d209c7de4bdaa3aef8746
Author: Julian Richen <julian richen io>
Date:   Sat Aug 28 15:25:06 2021 -0400

    AdwApplication: Fix memory leak in update_stylesheet
    
    GtkSettings::gtk-theme-name, or any property returned by GtkSettings'
    get_property, is g_value_copy-ed to the provided variable (theme_name).
    Switching const char to a g_autofree gchar * to automatically free the
    variable once out of scope.

 src/adw-application.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/adw-application.c b/src/adw-application.c
index be283290..4a1ae76f 100644
--- a/src/adw-application.c
+++ b/src/adw-application.c
@@ -70,7 +70,7 @@ update_stylesheet (AdwApplication *self)
 {
   AdwApplicationPrivate *priv = adw_application_get_instance_private (self);
   gboolean is_dark, is_hc, is_hc_dark;
-  const char *theme_name;
+  g_autofree gchar *theme_name;
 
   g_object_get (gtk_settings_get_default (),
                 "gtk-theme-name", &theme_name,