Behat error 'Warning: Undefined array key 1' on Moodle 4.5

[abias]

On Moodle 4.5, every now and then a particular Behat error appears:

001 Scenario: Setting: Information banners - Reset dismissed info banner 1          # /home/runner/work/moodle-theme_boost_union/moodle-theme_boost_union/moodle/theme/boost_union/tests/behat/theme_boost_union_contentsettings_infobanners.feature:179
      And I navigate to "Appearance > Boost Union > Content" in site administration # /home/runner/work/moodle-theme_boost_union/moodle-theme_boost_union/moodle/theme/boost_union/tests/behat/theme_boost_union_contentsettings_infobanners.feature:197
        Warning: Undefined array key 1 in /home/runner/work/moodle-theme_boost_union/moodle-theme_boost_union/moodle/lib/behat/classes/behat_session_trait.php line 971

Running the Behat job again mostly fixes the issue, but this should be investigated anyway.

[abias]

This is really strange as the core_sms subsystem which should be initialized here is not related or manipulated by Boost Union in any way.

Looking closer at the initialization of the core_sms\manager, I saw that this is done with di which we manipulate in https://github.com/moodle-an-hochschulen/moodle-theme_boost_union/blob/main/lib.php#L664. However, even if this line is commented, the Behat failure persists.

On the other hand, it seems not to be a Moodle core issue as the Behat failure seems not to happen if the scenario is tested on Boost Core.

The only thing which I could find out in the available time is that the Behat failure will vanish if caches are purged before navigating to the content settings.

I will create a PR for that.