--- xmlsitemap.admin.inc	2010-05-15 12:02:25.000000000 +0300
+++ diff-xmlsitemap.admin.inc	2010-05-15 12:22:04.474411351 +0300
@@ -818,6 +818,7 @@ function xmlsitemap_add_form_link_option
     ctools_include('dependent');
   }
 
+  !empty($form['#submit']) && is_array($form['#submit']) or $form['#submit'] = array();
   // Add the submit handler to adjust the default values if selected.
   if (!in_array('xmlsitemap_process_form_link_options', $form['#submit'])) {
     array_unshift($form['#submit'], 'xmlsitemap_process_form_link_options');