Undefined index: label in class.ctct_process_form.php

Hi Friends, When sending a form(Newsletter) without data generates the following message:

<b>Notice</b>: Undefined index: label in <b>local-path/wp-content/plugins/constant-contact-api/classes/class.ctct_process_form.php</b> on line <b>232</b>

Thanks

https://ww.wp.xz.cn/plugins/constant-contact-api/