Fatal error messgae printed on note but no order details

Now I have the notes printing I get:

Fatal error: Call to a member function exists() on a non-object in /home/thedally/public_html/winkdemo.info/wp-content/plugins/woocommerce-delivery-notes/classes/class-wcdn-print.php on line 162

Without any order or invoice details,

Can anyone help help or make suggestions Please.

Thanks
Chris

http://wordpress.org/extend/plugins/woocommerce-delivery-notes/