PHP error

When trying to save a widget, backend crashes and this error: Internal Server Error The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator to inform of the time the error occurred and of anything you might have done that may have caused the error. More information about this error may be available in the server error log. The error log is full of this: mod_fcgid: stderr: PHP Warning: count(): Parameter must be an array or an object that implements Countable in /path-to-site/wp-content/plugins/addon-so-widgets-bundle/cmb/init.php on line 746