down function was missing

application/migrations/159_extend_default_qsl.php

@@ -1,11 +1,16 @@
 <?php
 
 // Create migration that makes the submode column in the logbook table an index
-class Migration_extend_default_qsl  extends CI_Migration {
+class Migration_extend_default_qsl  extends CI_Migration
+{
 
-    public function up() {
+    public function up()
+    {
         $this->db->query("ALTER TABLE `users` CHANGE COLUMN `user_default_confirmation` `user_default_confirmation` VARCHAR(4) NULL DEFAULT NULL");
     }
-}
 
-?>
+    public function down()
+    {
+        //the down function can be empty here, but we need one. 
+    }
+}