[gthumb] thumbnailer: fixed variable name

[Paolo Bacchilega <paobac src gnome org>]

commit 057d36c605ab8a10699bba2433f0411d1fbdae28
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Sun Apr 3 10:26:06 2022 +0200

    thumbnailer: fixed variable name

 gthumb/gnome-desktop-thumbnail.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gthumb/gnome-desktop-thumbnail.c b/gthumb/gnome-desktop-thumbnail.c
index d0568637..cc27cc94 100644
--- a/gthumb/gnome-desktop-thumbnail.c
+++ b/gthumb/gnome-desktop-thumbnail.c
@@ -869,7 +869,7 @@ gnome_desktop_thumbnail_factory_new (GnomeDesktopThumbnailSize size)
 
   if (!factory->priv->use_xdg_dir) {
     char *old_cache_dir = g_build_filename (g_get_home_dir (), ".thumbnails", NULL);
-    factory->priv->use_xdg_dir = !g_file_test (xdg_directory, G_FILE_TEST_EXISTS);
+    factory->priv->use_xdg_dir = !g_file_test (old_cache_dir, G_FILE_TEST_EXISTS);
   }
 
 #endif