Index: xmlsitemap_menu.module
===================================================================
--- xmlsitemap_menu.module	(revision 344)
+++ xmlsitemap_menu.module	(working copy)
@@ -30,7 +30,7 @@
       $form['xmlsitemap_menu']['xmlsitemap_menu_menus'] = array(
         '#type' => 'checkboxes',
         '#title' => t('Menus to include in sitemap'),
-        '#default_value' => variable_get('xmlsitemap_menu_menus', array()),
+        '#default_value' => array_filter(variable_get('xmlsitemap_menu_menus', array())),
         '#options' => menu_get_root_menus(),
         '#checkall' => TRUE,
       );