Warning: First parameter must either be an object or the name of an existing class in

Hey guys

I'm not sure why this error is suddenly appearing on my websites:

Warning: First parameter must either be an object or the name of an existing class in /home/bunobuno/public_html/wp-content/plugins/white-label-branding-multisite/includes/class.wlb_dashboard.php on line 537

Any clues?