Triggers warning upon activation.

Triggers the warning below upon activation, perhaps because WP is a sub-folder? –

Warning: array_key_exists() [function.array-key-exists]: The second argument should be either an array or an object in /home/therushc/public_html/trc/wp-content/plugins/wp-simple-booking-calendar/library/WpSimpleBookingCalendar/Model.php on line 82

https://www.ads-software.com/extend/plugins/wp-simple-booking-calendar/