diff -ru faceted_search/faceted_search.admin.inc faceted_search2/faceted_search.admin.inc
--- faceted_search/faceted_search.admin.inc	2009-03-11 21:31:19.000000000 +0000
+++ faceted_search2/faceted_search.admin.inc	2009-04-17 12:05:19.000000000 +0000
@@ -277,8 +277,11 @@
   drupal_write_record('faceted_search_env', $env, $update);
   
   // Save filter settings.
-  if ($form_state['values']['facets']) {
-    faceted_search_save_filter_settings($env->env_id, array_merge($form_state['values']['facets'], $form_state['values']['keyword_filters']));
+  if ($form_state['values']['facets'] || $form_state['values']['keyword_filters']) {
+    // if either is null, array_merge returns null
+    $facets = (is_null($form_state['values']['facets'])) ? array() : $form_state['values']['facets'];
+    $keywords = (is_null($form_state['values']['keyword_filters'])) ? array() : $form_state['values']['keyword_filters'];
+    faceted_search_save_filter_settings($env->env_id, array_merge($facets, $keywords));
   }
 
   // Rebuild the menus, if only for updating titles.