Notice: Trying to get property of non-objec

Hi – I use the plugin with woocommerce, when i first installed the plugin yesteday, everything was fine.

now today i receive:
Notice: Trying to get property of non-object in /homepages/21/d703445402/htdocs/clickandbuilds/B4Branded2/wp-content/plugins/woo-invoices/includes/output-filters.php on line 365

When i try to submit the quote/invoice via email.

It still sends the email but displays this above 6times before the email text area. which takes up alot of the page.