Blocks: Don't return null for string value

[obenland]

Fixes a bug where updating meta values ends up comparing different data types and failing.

Proposed changes:

• Always save a string for activitypub_content_warning, regardless if it's empty or not.

Other information:

• Have you written new tests for your changes, if applicable?

Testing instructions:

This is better tested on a site where the Jetpack plugin is installed, connected to WordPress.com, and where you've toggled the Newsletter feature on. All WordPress.com simple sites satisfy those requirements.

1. Go to Posts > Add New
2. Write a new post with some ActivityPub content, such as a Federated reply block with any ActivityPub-compatible content like https://mastodon.social/@pfefferle/114502331086451476.
3. Hit Publish
4. Before to confirm publication, check the Newsletter panel, and change the value to "Post only".
5. Hit Publish.
   • The post should be published with no errors.
   • You should see a Create event in the outbox.

Changelog entry

• Automatically create a changelog entry from the details below.

Changelog Entry Details

Significance

• Patch
• Minor
• Major

Type

• Added - for new features
• Changed - for changes in existing functionality
• Deprecated - for soon-to-be removed features
• Removed - for now removed features
• Fixed - for any bug fixes
• Security - in case of vulnerabilities

Message

Avoid type mismatch when updating activitypub_content_warning meta values.

[Copilot]

Pull Request Overview

Ensure the activitypub_content_warning post meta always stores a string by switching from a custom callback that could return null to the built-in sanitize_text_field.

• Removed anonymous sanitize callback returning null for empty values
• Switched to sanitize_text_field for consistent string output

Comments suppressed due to low confidence (1)

includes/class-blocks.php:46

• Add or update unit tests to confirm that the sanitize callback returns an empty string (rather than null) when no warning text is provided.

'sanitize_callback' => 'sanitize_text_field',

[jeherve]

This fixes the issue for me. 🚢