Fatal error: Uncaught Error: Class 'WP_Widget' not found in /srv/drbd-web/home/chelix/public_html/wp-content/plugins/all-in-one-event-calendar/app/view/embeddable.php on line 2

Error: Class 'WP_Widget' not found in /srv/drbd-web/home/chelix/public_html/wp-content/plugins/all-in-one-event-calendar/app/view/embeddable.php on line 2

Call Stack:
    0.0010     361016   1. {main}() /srv/drbd-web/home/chelix/public_html/wp-content/plugins/all-in-one-event-calendar/app/view/embeddable.php:0