Error with custom cert pluging

[EiffelD]

When trying to reposition elements for the custom cert plugin, we noticed the following error:

Error
Exception - htmlspecialchars(): Argument #1 ($string) must be of type string, action_link given

Debug info:
Error code: generalexceptionmessage

Stack trace:

line 100 of /lib/weblib.php: TypeError thrown

line 100 of /lib/weblib.php: call to htmlspecialchars()

line 1713 of /lib/outputcomponents.php: call to s()

line 1727 of /lib/outputcomponents.php: call to html_writer::attribute()

line 1656 of /lib/outputcomponents.php: call to html_writer::attributes()

line 1645 of /lib/outputcomponents.php: call to html_writer::start_tag()

line 1779 of /lib/outputcomponents.php: call to html_writer::tag()

line 2056 of /theme/snap/classes/output/core_renderer.php: call to html_writer::link()

line 53 of /theme/snap/layout/default.php: call to theme_snap\output\core_renderer->snapnavbar()

line 1401 of /lib/outputrenderers.php: call to include()

line 1331 of /lib/outputrenderers.php: call to core_renderer->render_page_layout()

line 138 of /mod/customcert/rearrange.php: call to core_renderer->header()

We changed the theme to another default theme and it worked. Can you advise how to resolve this?

Moodle:3.11.13

[EiffelD]

Changing to a different theme works as expected.

[EiffelD]

We have changed to PHP v7.4 from 8.0 and noticed the problem is no longer occurring. Is there a timeline when the theme will be PHP 8.0 compliant as PHP 7.4 is no longer receiving updates.