Bogus error messages

Warning: Creating default object from empty value in /srv/disk2/1171911/www/hjcs.org/wp-content/plugins/wp-calendar/fsCalendarAdmin.php on line 376

Warning: Creating default object from empty value in /srv/disk2/1171911/www/hjcs.org/wp-content/plugins/wp-calendar/fsCalendarAdmin.php on line 385

Warning: Creating default object from empty value in /srv/disk2/1171911/www/hjcs.org/wp-content/plugins/wp-calendar/fsCalendarEvent.php on line 69

One of these pops up whenever I add or edit an event. But more importantly, visitors to my site see it when they click on the Calendar from the main menu.

http://www.hjcs.org

https://wordpress.org/plugins/wp-calendar/