diff -r -u -F '^function' search_config_old/search_config.module search_config/search_config.module
--- search_config_old/search_config.module	2007-05-21 16:18:38.000000000 +0200
+++ search_config/search_config.module	2007-05-21 12:57:08.000000000 +0200
@@ -110,19 +110,27 @@ function search_config_form_alter($form_
                   unset($taxonomy[$vocab][$k]);
                 }
               }
+              // Remove empty vocabs
+              if (count($taxonomy[$vocab]) == 0) {
+                unset($taxonomy[$vocab]);
+              }
             }
 
-            // Taxonomy box:
-            $form['advanced']['category'] = array(
-              '#type' => 'select',
-              '#title' => t('Only in the category(s)'),
-              '#prefix' => '<div class="criterion">',
-              '#size' => 10,
-              '#suffix' => '</div>',
-              '#options' => $taxonomy,
-              '#multiple' => TRUE,
-            );
-
+            if (count($taxonomy) == 0) {
+              unset($form['advanced']['category']);
+            }
+            else {
+              // Taxonomy box:
+              $form['advanced']['category'] = array(
+                '#type' => 'select',
+                '#title' => t('Only in the category(s)'),
+                '#prefix' => '<div class="criterion">',
+                '#size' => 10,
+                '#suffix' => '</div>',
+                '#options' => $taxonomy,
+                '#multiple' => TRUE,
+              );
+            }
           }
         }
       }