Patch submitted by Ethem:

Error message isn't shown when user clicked without key.
Multienrol is enabled (course enrol key with authorize)

This patch allows showing error message when user clicked button without key.

enrol/authorize/enrol.php

@@ -132,7 +132,7 @@ class enrolment_plugin_authorize
     {
         global $CFG;
 
-        if (zero_cost($course) || (!empty($course->password) && !empty($form->password))) {
+        if (zero_cost($course) || (!empty($course->password) && !empty($form->password) && $form->enrol == 'manual')) {
             $manual = enrolment_factory::factory('manual');
             $manual->check_entry($form, $course);
             if (!empty($manual->errormsg)) {

enrol/manual/enrol.html

@@ -20,6 +20,7 @@
             <td>
               <input type="password" name="password" size="20" value="<?php p($password) ?>"  />
               <input type="hidden" name="id" value="<?php p($course->id) ?>"  />
+              <input type="hidden" name="enrol" value="manual" />
               <input type="submit" value="<?php print_string("enrolme") ?>" />
             </td>
           </tr>