Undefined property

I'm getting this error message when submitting a category in the dashboard
Undefined property: stdClass::$show_on_submit_event_form

There are subsequent errors on the display as well.. .

1. Go to Events Booking -> Configuration, save the configuration data (just press Save button in the toolbar) and the error like that will be gone

2. Go to Events Booking -> Configuration, find the config option Debug Mode, set it to No, too

Regards,

Tuan