Pull Request resolves #48313.

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

Preserve the original Registry instance for the article model's params state while building month-filter options.

Testing Instructions

1. In Content Options, set List Layouts > Filter Field to Month.
2. Open a category blog or list layout that uses the setting.
3. Confirm the page renders and the month filter is available.

Actual result BEFORE applying this Pull Request

The state-copy loop turns the nested params Registry into an array. The article model then fails when it calls get() on that state.

Expected result AFTER applying this Pull Request

The article model retains the original params Registry, so category listings render with the month filter enabled.

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed

Verification

• ./libraries/vendor/bin/phpunit --configuration phpunit.xml.dist tests/Unit/Libraries/Cms/Html/ContentTest.php
• ./libraries/vendor/bin/php-cs-fixer fix -vvv --dry-run --diff
• ./libraries/vendor/bin/phpcs --extensions=php -p --standard=ruleset.xml .