Undefined index: USER [#3239218]

Problem/Motivation

When using the Guardian module in CI tests, I get the following error:

Undefined index: USER
/htdocs/modules/contrib/guardian/src/GuardianManager.php:185
/htdocs/modules/contrib/guardian/src/GuardianManager.php:145
/htdocs/modules/contrib/guardian/guardian.install:59

Steps to reproduce

Install the guardian module in a functional Drupal test.

Proposed resolution

Fix the notice.

Remaining tasks

Create patch.

User interface changes

None.

API changes

None.

Data model changes

None.

Issue fork guardian-3239218

Show commands

Start within a Git clone of the project using the version control instructions.

Add & fetch this issue fork’s repository

Or, if you do not have SSH keys set up on git.drupalcode.org:

Add & fetch this issue fork’s repository

3239218-undefined-index-user changes, plain diff MR !1
Check out this branch for the first time

Check out existing branch, if you already have it locally