Grunion Contact Form: If there are no options for the current select or radio group, default the optionCount index to 1; else the first item is dropped from the list when the form is added to the page.

See http://[private link]

Merges r97966-wpcom.
Rest API: Fix error return from /batch
This commit fixes how the /batch endpoint reports errors for
individual API calls. Formerly, errors were being suppressed entirely,
but now they will be returned as an object with the shape:
{
  status_code: $the_status,
  errors: $the_wp_error
}
if an individual API call in the batch returns an WP_Error.

This fix matches the expectation of the meta batch test.

Merges r97969-wpcom.