Bug 1479434: $SESSION undefined for validation step

Need to have $SESSION available to be able to send error to it

behatnotneeded

Change-Id: Ie298c95a8ef9a4fdc5589a6934110fc86c1e771d
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>
(cherry picked from commit 7b212c53)

htdocs/admin/users/progressbar.php

@@ -161,7 +161,7 @@ $form = pieform(array(
 ));
 
 function progressbarform_validate(Pieform $form, $values) {
-    global $USER;
+    global $SESSION, $USER;
     $inst = $values['institution'];
     if (empty($inst) || !$USER->can_edit_institution($inst)) {
         $SESSION->add_error_msg(get_string('notadminforinstitution', 'admin'));