interest groups warning

Hi all!

If I'm using interest groups than when I'm subscribing to a mailchimp list than a warning returned:
Warning: Invalid argument supplied for foreach() mailchimp_signup_subscribe_form_submit() függvényben (/home/shl/public_html/sites/all/modules/contrib/mailchimp/modules/mailchimp_signup/mailchimp_signup.module 386 sor).

It's caused by a foreach in mailchimp_signup_subscribe_form_submit():

    foreach ($interest_groups as $interest_group) {
      dsm($interest_group); // <--- custom debugging
      foreach ($interest_group as $interest_id => $interest_status) {
        $interests[$interest_id] = ($interest_status !== 0);
      }
    }

dsm() prints $interest_group, but it is not an array only a string

this workaround solves the problem for me:

function MYMODULE_form_mailchimp_signup_subscribe_block_newsletter_form_alter(&$form, &$form_state, $form_id) {
  ...
  $form['#validate'][] = 'MYMODULE_form_mailchimp_signup_subscribe_block_newsletter_form_validate';
}
function MYMODULE_form_mailchimp_signup_subscribe_block_newsletter_form_validate($form, &$form_state) {
  if (
    isset($form_state['values']['mailchimp_lists']['interest_groups']) &&
    !empty($form_state['values']['mailchimp_lists']['interest_groups'])
  ) {
    foreach ($form_state['values']['mailchimp_lists']['interest_groups'] as $ig_key => $ig) {
      $form_state['values']['mailchimp_lists']['interest_groups'][$ig_key] = array($ig => 1);
    }
  }
}

mailchimp version: 7.x-4.7+1-dev