Mailchimp API connection error handling

[miguelpeixe]

It's not always guaranteed that the response body from Mailchimp is an array, as assumed here:

newspack-plugin/includes/oauth/class-mailchimp-api.php

Lines 167 to 172 in 9fd3e53

	$parsed_response = json_decode( $response['body'], true );
	return new \WP_Error(
	'newspack_mailchimp_api',
	array_key_exists( 'title', $parsed_response ) ? $parsed_response['title'] : __( 'Request failed.', 'newspack' )
	);

It can fail with:

PHP Fatal error:  Uncaught TypeError: array_key_exists(): Argument #2 ($array) must be of type array, null given in newspack-plugin/includes/oauth/class-mailchimp-api.php:171

A more generic error handling is suited for when the response body is unavailable.