Gravity Forms MailChimp Add-On was updated to version 3.2, from version 3.1. Changelog:

• Added hook to allow args to be changed before sending submission to MailChimp.
• Added hook to select whether empty mapped fields should override existing values on Mailchimp; defaults to override.
• Fixed issue where existing groups were not maintained for users already subscribed.
• Fixed debug notice messages.
• Fixed fatal error displayed on certain situations.