MODX 3 modUser class joinGroup() crashes is $_SESSION is not set

[BobRay]

Bug report

Summary

Quick summary what's this issue about.

Calling $user->joinGroup() with no $_SESSION set crashes.

Here's the offending code (line 716 of core/model/modx/moduser.class.php):

                     unset($_SESSION["modx.user.{$this->get('id')}.userGroupNames"],
                     $_SESSION["modx.user.{$this->get('id')}.userGroups"]);

This breaks acceptance tests that run in the MODX Manager.

Environment

MODX version, MODX 2.8.1

[BobRay]

I would propose the fix of adding this line just above the unset call:

$_SESSION = isset($_SESSION)? $_SESSION : array();

[sergant210]

$_SESSION["modx.user.{$this->get('id')}.userGroupNames" - this code is legacy. It must be removed. All permission logic must be removed from the session.

[Ibochkarev]

Fixed #15376