Perch Runway 3.1.3 backup to Amazon S3 error/warning

I first came across an error when I switched my Perch Runway sites to PHP 7.1. I've now switched them to PHP 7.2.12 and got the same problem albeit with S3 and not DropBox. The previous thread is here - https://forum.grabaperch.com/forum/04-03-2017-runway-backups-to-dropbox-have-stopped

I had my host set 'allow_url_fopen' set to 'on' for the PHP 7.2 handler and this fixed the problem. Without it, you get this error on backups ...

failed to open stream: no suitable wrapper could be found
/home/xxxxx/public_html/perch/core/runway/lib/PerchBackupPlan.class.php

So, now the backup works and it appears on my Amazon S3 storage. But I see this error/warning on the Runway Admin backup page. It doesn't appear to stop the backup working but might be important to know about?

Array
(
    [type] => 2
    [message] => count(): Parameter must be an array or an object that implements Countable
    [file] => /home/xxxxxx/public_html/perch/core/runway/apps/perch_s3/lib/guzzlehttp/guzzle/src/Handler/CurlFactory.php
    [line] => 67
)

Here's my diagnostics if helpful ...

Perch Runway: 3.1.3, PHP: 7.2.12, MySQL: mysqlnd 5.0.12-dev - 20150407 - $Id: 38fea24f2847fa7519001be390c98ae0acafe387 $, with PDO
Server OS: Linux, cgi-fcgi
Installed apps: content (3.1.3), assets (3.1.3), categories (3.1.3), perch_members (1.6.4), redfinch_logger (1.0.1), pipit_test (0.1)
App runtimes: <?php $apps_list = [ 'perch_members', ];
PERCH_LOGINPATH: /perch
PERCH_PATH: /home/xxxxxx/public_html/perch
PERCH_CORE: /home/xxxxxx/public_html/perch/core
PERCH_RESFILEPATH: /home/xxxxxx/public_html/perch/resources
Image manipulation: GD
PHP limits: Max upload 20M, Max POST 20M, Memory: 128M, Total max file upload: 20M
F1: 3b606135b33e6a102526838f4152a807
Resource folder writeable: Yes
DOCUMENT_ROOT: /home/xxxxxx/public_html
HTTP_HOST: www.xxxxxx.org.uk
REQUEST_URI: /perch/core/settings/diagnostics/
SCRIPT_NAME: /perch/core/settings/diagnostics/index.php