PHP Error With BPress Group Calendar Plugin

Fatal error: Class 'BP_Group_Extension' not found in /home/eslwebpo/public_html/neatexamprep/wp-content/plugins/bp-group-calendar/groupcalendar/bp-group-calendar.php on line 103

Got this when I changed a basic setting in core bp. Now I'm kind of locked out as the error won't allow me to change pages. Thanks! Any way to get a quick fix out on this one? Cheers.