e-newsletter causing php error

Hi there,

My debug.log is filled with these errors:

[21-Jun-2016 10:16:51 UTC] PHP Notice: Trying to get property of non-object in /xxx/xxx/xxx/wp-content/plugins/e-newsletter/email-newsletter-files/builder/class.builder.php on line 368

What could I do to try and resolve this?

Thanks - Mark