Notes: Fix warning in comment content check

[Mamaduka]

What?

Part of #73141.

PR tries to fix warning triggered by check_is_comment_content_allowed call inside the ::update_item controller method. The warning is logged when the note is resolved or reopened.

This doesn't look like a new issue, it just more visible with Notes.

PHP Warning: Undefined array key "comment_content" in ~/gutenberg/wp-content/plugins/gutenberg/lib/compat/wordpress-6.9/class-gutenberg-rest-comment-controller-6-9.php on line 604

Why?

Users can sent partial data when updating a comment/note, this includes omitting the content. The ::update_item should account for this.

• ::create_item sets content value to empty string when it's not included in the request. We can't do this when updating the item.
• ::update_item has special check for when only comment status is changed, that code path never runs. The $prepared_args always includes fallback values for user ID and agent. I would like to fix this separately, will create the trac ticket.

Testing Instructions

1. Open post or page with notes.
2. Try resolving or reopning a note.
3. Confirm PHP warnings aren't logged.

Testing Instructions for Keyboard

Same.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[Mamaduka]

This changes behavior described in comment, but it doesn't affect anything actual.

[Mamaduka]

I just realized this doesn't require fix in core. Props to @kadamwhite - Mamaduka/wordpress-develop@1c9e7ef.

I'll create track ticket for "::update_item has special check for when only comment status is changed"

Here's the ticket - https://core.trac.wordpress.org/ticket/64248#ticket.