Notice: Undefined index: xmlsitemap in xmlsitemap_link_bundle_settings_form_submit() (line 1315 of xmlsitemap.module)

Trivial patch to avoid an "Undefined index" notice.

--- xmlsitemap.module
+++ xmlsitemap.module
@@ -1312,6 +1312,9 @@ function xmlsitemap_link_bundle_settings_form_submit($form, &$form_state) {
     }
   }
 
+  if (empty($form_state['values']['xmlsitemap'])) {
+    return;
+  }
   xmlsitemap_link_bundle_settings_save($entity, $bundle, $form_state['values']['xmlsitemap']);
 
   $entity_info = $form['xmlsitemap']['#entity_info'];