Fix: Guard against wp_parse_url() returning false in Pagination_Helper

[ProjectEli]

Context

When wp_parse_url() receives a malformed URL (e.g., http:/// caused by a missing Host header), it returns false instead of an array. The subsequent array_key_exists('query', false) call throws a TypeError on PHP 8.x, resulting in a fatal error.

Summary

This PR can be summarized in the following changelog entry:

• Fixes a bug where a fatal TypeError occurred in pagination-helper.php when wp_parse_url() returned false due to a malformed URL (e.g., requests without a Host header on Bitnami WordPress environments).

Relevant technical choices:

• Added an early return guard clause (if ( ! is_array( $url_parts ) ) return $url;) before accessing the parsed URL array. This is the minimal, defensive fix that preserves existing behavior for all valid URLs while gracefully handling the edge case.

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

1. Set up a WordPress instance with PHP 8.x and Yoast SEO installed.
2. Temporarily modify wp-config.php to set WP_HOME to a malformed URL such as http:/// (simulating a missing Host header scenario).
3. Visit any frontend page that triggers pagination (e.g., a blog archive with multiple pages).
4. Before fix: A fatal TypeError is thrown at pagination-helper.php:74.
5. After fix: The page loads without error; the original URL is returned as-is when parsing fails.
6. Revert WP_HOME to its normal value and confirm pagination still works correctly on archive pages.

Relevant test scenarios

• Changes should be tested with the browser console open
• Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
• Changes should be tested on different editors
• Changes should be tested on different browsers
• Changes should be tested on multisite

Console should show no PHP errors or warnings after the fix is applied.

Test instructions for QA when the code is in the RC

• QA should use the same steps as above.

Impact check

This PR affects the following parts of the plugin, which may require extra testing:

• src/helpers/pagination-helper.php — specifically the get_paginated_url() method. Regression testing should confirm that normal pagination (rel next/prev) continues to work on archive and paginated pages.

Quality assurance

• I have tested this code to the best of my abilities.
• During testing, I had activated all plugins that Yoast SEO provides integrations for.
• I have added unit tests to verify the code works as intended.
• I have checked that the base branch is correctly set.

Innovation

• No innovation project is applicable for this PR.

Fixes #23057