Error messages after Installation

After installation I am getting the error messages in settings => customers

Notice: wpdb::prepare was called incorrectly. The query only expected one placeholder, but an array of multiple placeholders was sent.

and in settings => bookings

Notice: Trying to get property of non-object in /www/htdocs/w017656d/wp-content/plugins/salon-booking-system/src/SLN/Metabox/Abstract.php on line 30

How can I get rid of this error messages?

• This topic was modified 8 years, 6 months ago by cinematic.