Call to undefined function admin_url() in /widgets/class-wp-widget-media.php:506

Olá a todos,

Um cliente escreveu-me com um erro critico no site. Estive a ver e já desativei todos os plugin e mudei o tema para o twentytwentfour e não consigo acesso ao admin. O wp-config parece-me bem, não vejo nada de estranho no site mas nunca tive um erro destes que não tivesse conseguido resolver, mas este está estranho. Já apaguei o class-wp-widget-media.php e fui buscar o novo ao repositório.

Não percebo muito bem o que se passa. O erro completo está em baixo. Alguma ideia?

Fatal error: Uncaught Error: Call to undefined function admin_url() in /home/hangarco/public_html/wp-includes/widgets/class-wp-widget-media.php:506 Stack trace: #0 /home/hangarco/public_html/wp-includes/widgets/class-wp-widget-media.php(85): WP_Widget_Media::get_l10n_defaults() #1 /home/hangarco/public_html/wp-includes/widgets/class-wp-widget-media-audio.php(26): WP_Widget_Media->__construct() #2 /home/hangarco/public_html/wp-includes/class-wp-widget-factory.php(62): WP_Widget_Media_Audio->__construct() #3 /home/hangarco/public_html/wp-includes/widgets.php(123): WP_Widget_Factory->register() #4 /home/hangarco/public_html/wp-includes/widgets.php(1835): register_widget() #5 /home/hangarco/public_html/wp-includes/class-wp-hook.php(324): wp_widgets_init() #6 /home/hangarco/public_html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() #7 /home/hangarco/public_html/wp-includes/plugin.php(517): WP_Hook->do_action() #8 /home/hangarco/public_html/wp-settings.php(705): do_action() #9 /home/hangarco/public_html/wp-config.php(87): require_once(‘/home/hangarco/…’) #10 /home/hangarco/public_html/wp-load.php(50): require_once(‘/home/hangarco/…’) #11 /home/hangarco/public_html/wp-blog-header.php(13): require_once(‘/home/hangarco/…’) #12 /home/hangarco/public_html/index.php(17): require(‘/home/hangarco/…’) #13 {main} thrown in /home/hangarco/public_html/wp-includes/widgets/class-wp-widget-media.php on line 506