Warning: Trying to access array offset on value of type bool in /home/.sites/821/site956/web/wp-includes/theme.php on line 2241

Fatal error: Uncaught ArgumentCountError: Too few arguments to function WP_Widget::__construct(), 0 passed in /home/.sites/821/site956/web/wp-includes/class-wp-widget-factory.php on line 100 and at least 2 expected in /home/.sites/821/site956/web/wp-includes/class-wp-widget.php:162
Stack trace:
#0 /home/.sites/821/site956/web/wp-includes/class-wp-widget-factory.php(100): WP_Widget->__construct()
#1 /home/.sites/821/site956/web/wp-includes/widgets.php(115): WP_Widget_Factory->register('Twenty_Eleven_E...')
#2 /home/.sites/821/site956/web/wp-content/themes/trachtenverein/functions.php(372): register_widget('Twenty_Eleven_E...')
#3 /home/.sites/821/site956/web/wp-includes/class-wp-hook.php(286): twentyeleven_widgets_init('')
#4 /home/.sites/821/site956/web/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array)
#5 /home/.sites/821/site956/web/wp-includes/plugin.php(453): WP_Hook->do_action(Array)
#6 /home/.sites/821/site956/web/wp-includes/widgets.php(1649): do_action('widgets_init')
#7 /home/.sites/821/site956/web/wp-includes/class-wp-hook.php(286): wp_widgets_init('')
#8 /home/.sites/821/site956/web/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array)
#9 /home/.sites/821/site956/web/wp-includes/plugin.php(453): WP_Hook->do_action(Array)
#10 /home/.sites/821/site956/web/wp-settings.php(450): do_action('init')
#11 /home/.sites/821/site956/web/wp-config.php(88): require_once('/home/.sites/82...')
#12 /home/.sites/821/site956/web/wp-load.php(37): require_once('/home/.sites/82...')
#13 /home/.sites/821/site956/web/wp-blog-header.php(13): require_once('/home/.sites/82...')
#14 /home/.sites/821/site956/web/index.php(17): require('/home/.sites/82...')
#15 {main}
  thrown in /home/.sites/821/site956/web/wp-includes/class-wp-widget.php on line 162