Not working anymore

After a long time of enjoyment with the plugin it’s not woking anymore. It’s not sending any email and I’m getting this message:

Parameter must be an array or an object that implements Countable in /home/customer/www/coherence.nl/public_html/wp-content/plugins/wp-email-users/wp-email-functions.php on line 80

Can You please help me?

Jacques

The page I need help with: [log in to see the link]