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

• line 713 of /lib/outputlib.php: call to debugging()
• line 1552 of /lib/pagelib.php: call to theme_config::load()
• line 687 of /lib/pagelib.php: call to moodle_page->initialise_theme_and_output()
• line 874 of /lib/pagelib.php: call to moodle_page->magic_get_theme()
• line 99 of /index.php: call to moodle_page->get_renderer()