MDL-30623 fix password upgrade path from 1.9

enrol/guest/db/install.php

@@ -0,0 +1,35 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Guest enrol plugin installation.
+ *
+ * @package    enrol
+ * @subpackage guest
+ * @copyright  2011 Petr Skoda  {@link http://skodak.org}
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+function xmldb_enrol_guest_install() {
+    global $CFG, $DB;
+
+    // migrate settings during 2.0 upgrade
+
+    // convert all null passwords to empty strings
+    $DB->set_field('enrol', 'password', '', array('enrol'=>'guest', 'password'=>null));
+}