Author, Author Name block: fix PHP warning error when there is no context

[t-hamano]

What?

Follow-up #67136
Closes #69948

Why?

Fixes PHP warning error when the Author and Author Name block have no context.

See #69948

How?

Checks for the existence of a context. If it doesn't, it continues with further processing. That is, if the block isn't relevant for a particular post type, it will be rendered.

However, the User REST API doesn't allow listing users if they have no posts written yet. As a follow-up, we may also need to add a check for the number of posts a user has written, in accordance with the REST API specification, in both blocks.

Testing Instructions

• Add a new user with the "Editor" role (This user has no posts).
• Add an Author Archives template:

<main class="wp-block-group">
<!-- wp:query-title {"type":"archive"} /-->
<!-- wp:post-author /-->
<!-- wp:post-author-name /-->
</main>
<!-- /wp:group -->

• Access http://localhost:8888/?author=2 (Change the author param value to the actual user id for the newly added user)
• Confirm that two blocks are rendered correctly and no PHP warning logs are displayed.

[github-actions]

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Co-authored-by: t-hamano <[email protected]>
Co-authored-by: Mamaduka <[email protected]>

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[Mamaduka]

However, the User REST API doesn't allow listing users if they have no posts written yet. As a follow-up, we may also need to add a check for the number of posts a user has written, in accordance with the REST API specification, in both blocks.

That condition has its problems and might change in the future. See: #69921

[t-hamano]

@Mamaduka Thanks for the review!

I'd like to add @justlevine, who first reported this issue on Slack, to the props list: https://wordpress.slack.com/archives/C02QB2JS7/p1744930825415699

[Mamaduka]

Of course! This would be their WP contribution email.

Co-authored-by: justlevine <[email protected]>

[t-hamano]

A backport PR for the wp/6.8 branch: #70001

[t-hamano]

Removing the Backport to WP Minor Release label as #70001 has just been merged into the wp/6.8 branch.