This page should be using theme boost_union which cannot be initialised. Nor can the site theme boost_union. Falling back to boost

• line 460 of /lib/classes/output/theme_config.php: call to debugging()
• line 1847 of /lib/pagelib.php: call to core\output\theme_config::load()
• line 108 of /lib/classes/output/bootstrap_renderer.php: call to moodle_page->initialise_theme_and_output()
• line 391 of /login/index.php: call to core\output\bootstrap_renderer->__call()