Undefined index error

Hi, I recently began getting the following error when someone submits a webform:

Notice: Undefined index: value in webform_mailchimp_webform_submission_insert() (line 42 of /sites/all/modules/webform_mailchimp/webform_mailchimp.module).

The error appears to have happened when I upgraded to the 7.x-4.0-alpha4 webform module in order to take advantage of some new functionality. Can anyone help?

Thanks.