login: Changing passwords now works when logged in as guest

login/change_password.php

@@ -99,7 +99,7 @@
     // We NEED to set this, because the form assumes it has a value!
     $frm->id = empty($course->id) ? 0 : $course->id;
 
-    if (empty($frm->username)) {
+    if (empty($frm->username) && !isguest()) {
         $frm->username = $USER->username;
     }
 

login/change_password_form.html

@@ -26,7 +26,7 @@
 <tr valign="top">
     <td><?php print_string("username") ?>:</td>
     <td>
-    <?php if (isadmin()) { ?>
+    <?php if (isadmin() || empty($frm->username)) { ?>
         <input type="text" name="username" size="25" value="<?php p($frm->username) ?>" alt="<?php print_string("username") ?>" />
     <?php } else { ?>
         <input type="hidden" name="username" value="<?php p($frm->username)?>" />  <?php p($frm->username)?>