Mailchimp connected in API response after disconnecting Jetpack

[adekbadek]

Steps to reproduce the issue

1. Connect, then disconnect Jetpack
2. Make a request to /wp-json/wpcom/v2/mailchimp
3. Observe that the response states Mailchimp is connected
4. Observe the connect_url link in the response directing to a blank page on wordpress.com

What I expected

Expected to see an unavailable_site_id error, as it is before connecting Jetpack.