Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, function "_wp_block_theme_register_classic_sidebars" not found or invalid function name in /homepages/19/d4296890325/htdocs/wordpress/wp-includes/class-wp-hook.php:308 Stack trace: #0 /homepages/19/d4296890325/htdocs/wordpress/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters('', Array) #1 /homepages/19/d4296890325/htdocs/wordpress/wp-includes/plugin.php(517): WP_Hook->do_action(Array) #2 /homepages/19/d4296890325/htdocs/wordpress/wp-includes/widgets.php(1854): do_action('widgets_init') #3 /homepages/19/d4296890325/htdocs/wordpress/wp-includes/class-wp-hook.php(308): wp_widgets_init('') #4 /homepages/19/d4296890325/htdocs/wordpress/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters(NULL, Array) #5 /homepages/19/d4296890325/htdocs/wordpress/wp-includes/plugin.php(517): WP_Hook->do_action(Array) #6 /homepages/19/d4296890325/htdocs/wordpress/wp-settings.php(623): do_action('init') #7 /homepages/19/d4296890325/htdocs/wordpress/wp-config.php(189): require_once('/homepages/19/d...') #8 /homepages/19/d4296890325/htdocs/wordpress/wp-load.php(50): require_once('/homepages/19/d...') #9 /homepages/19/d4296890325/htdocs/wordpress/wp-blog-header.php(13): require_once('/homepages/19/d...') #10 /homepages/19/d4296890325/htdocs/wordpress/index.php(17): require('/homepages/19/d...') #11 {main} thrown in /homepages/19/d4296890325/htdocs/wordpress/wp-includes/class-wp-hook.php on line 308