Book module "Printer Friendly version" return error.

Problem/Motivation

In both Book 1.0.0 and in Book 2.0.0-alpha1 I am getting the following error whenever "Printer Friendly Version" is clicked: "The website encountered an unexpected error. Try again later."

This error is persistent on several Drupal sites having the same general configuration.

The information in the Drupal database log:

Location https://example.com/book/export/html/5
Referrer https://example.com/content/some-book-url
Message Twig\Error\RuntimeError: The "filter" filter expects a sequence/mapping or "Traversable", got "integer". in Twig\Extension\CoreExtension::filter() (line 37 of /var/www/vhosts/example.com/site/web/themes/contrib/adaptivetheme/at_core/templates/layout/book-export-html.html.twig).

I have created this issue here because the error does not occur while using the Olivero theme on the same websites.

Steps to reproduce

Drupal 10.3.x, an Adaptive generated subtheme, and either Book 1.0.0 or Book 2.0.0-alpha1
Create and navigate to any book content node
Click the "Printer-friendly version" link below the content.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes