email_type is invalid

The email type that is being sent is empty.
I get an error code from mailchimp API with code 400
I made it as 'html' in the controller
Can you please specify the type of the email_type.

Thanks

[AxelPariss]

The same error, I submitted a pull request (you can check if you want to update your controller)

I replace

 'email_type' => $request->post('email_type', ''),

by

 'email_type' => empty($request->post('email_type', '')) ? $request->post('email_type', '') : 'text',

in
vendor/lukeyouell/craft-mailchimplists/src/controllers/SubscribeController.php