PHP 8 Warning: Undefined property

The following warning appears with each of the two examples and PHP 8.1.11:

[Thu Oct 13 11:31:11.434848 2022] [proxy_fcgi:error] [pid 29959] [client 127.0.0.1:44468] AH01071: Got error 'PHP message: PHP Warning:  Undefined property: helper_plugin_folded::$ids_count in /var/www/dokuwiki/lib/plugins/folded/helper.php on line 25'

Example code:

This is example ++text | with some of it only shown when you unfold it++. And after that
the text just continues to flow in the same paragraph.

This is example text.

++++ Title |

| This table | is only shown | when you unfold the block |

{{page>some other wiki page&inline}}

++++

Version information:

$ cat /etc/centos-release
CentOS Linux release 7.9.2009 (Core)
$ php --version
PHP 8.1.11 (cli) (built: Sep 28 2022 09:08:05) (NTS gcc x86_64)
Copyright (c) The PHP Group
Zend Engine v4.1.11, Copyright (c) Zend Technologies
$ cat dokuwiki/VERSION 
2022-07-31a "Igor"
$ grep date dokuwiki/lib/plugins/folded/plugin.info.txt 
date   2022-09-18

dokufreaks / plugin-folded

PHP 8 Warning: Undefined property #78