mySQL complaint in Appointments + plugin

I'm seeing this in php5_error_log but am not sure how to trigger it:
[12-Apr-2013 14:36:44 UTC] WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AND location=0' at line 1 for query SELECT * FROM wp_app_exceptions WHERE worker= AND location=0 made by require('wp-blog-header.php'), require_once('wp-includes/template-loader.php'), include('/themes/photocrati-theme/page.php'), the_content, apply_filters('the_content'), call_user_func_array, do_shortcode, preg_replace_callback, do_shortcode_tag, call_user_func, Appointments->monthly_calendar, Appointments->get_monthly_calendar, Appointments->is_holiday, Appointments->get_exception
[12-Apr-2013 14:50:11 UTC] WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AND location=0' at line 1 for query SELECT * FROM wp_app_working_hours WHERE worker= AND location=0 made by require('wp-blog-header.php'), require_once('wp-includes/template-loader.php'), include('/themes/photocrati-theme/page.php'), the_content, apply_filters('the_content'), call_user_func_array, do_shortcode, preg_replace_callback, do_shortcode_tag, call_user_func, Appointments->monthly_calendar, Appointments->get_monthly_calendar, Appointments->get_working_days, Appointments->get_work_break