Description

After the release of 21.8.0 we started getting test failures in wordpress-rs because the schema format for templates had changed.

I've narrowed it down to #72029, specifically this change. This check in #72141 seems to further contribute to the problem, as $post_arr['id'] is never an int for built-in templates.

Step-by-step reproduction instructions

1. Create a new WordPress site (it should use twentytwentyfive as the theme – this one has templates, so it'll demonstrate the problem)
2. Set up permalinks
3. Fetch wp-json/wp/v2/templates
4. Note that the theme field for each template is twentytwentyfive.
5. Install the "Gutenberg" plugin (21.8.0 or greater)
6. Fetch wp-json/wp/v2/templates
7. Note that the theme field for each template is null
8. Comment out lines 35-53 (inclusive) in wp-content/plugins/gutenberg/lib/compat/wordpress-6.9/template-activate.php
9. Fetch wp-json/wp/v2/templates
10. Note that the theme field for each template is twentytwentyfive.

Screenshots, screen recording, code snippet

No response

Environment info

• WP 6.8.3
• Gutenberg 21.8.0

Please confirm that you have searched existing issues in the repo.

• Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

• Yes

Please confirm which theme type you used for testing.

• Block
• Classic
• Hybrid (e.g. classic with theme.json)
• Not sure