Index: taxonomy.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/taxonomy.module,v
retrieving revision 1.257
diff -u -F^f -r1.257 taxonomy.module
--- taxonomy.module	29 Jan 2006 07:50:45 -0000	1.257
+++ taxonomy.module	3 Feb 2006 07:20:21 -0000
@@ -914,6 +914,10 @@ function _taxonomy_term_select($title, $
       $value = $tree[0]->tid;
     }
   }
+  if (!array_intersect((array)$value, array_keys($options))) {
+    // if there are no terms selected for this vocabulary, select default option
+    $value = 0;
+  }
   return array('#type' => 'select', '#title' => $title, '#default_value' => $value, '#options' => $options, '#description' => $description, '#multiple' => $multiple, '#size' => $multiple ? min(9, count($options)) : 0, '#weight' => -15, '#theme' => 'taxonomy_term_select');
 }