Installation of Subscribe Email Plugin Failed

I am getting is error message.

Warning: Invalid argument supplied for foreach() in /home/holidayp/public_html/coupon/wp-content/plugins/subscribe-by-email/model/model.php on line 428

Warning: Cannot modify header information - headers already sent by (output started at /home/holidayp/public_html/coupon/wp-content/plugins/subscribe-by-email/model/model.php:428) in /home/holidayp/public_html/coupon/wp-includes/pluggable.php on line 875

Please can you advise?

Thanks,

Chris.