Avoid a PHP Notice when render_block() is called without attributes.

[dd32]

Description

When render_block() is called without block attributes set, wp_render_elements_supports() causes a PHP Notice.

Example:

<?php echo render_block( array( 'blockName' => 'wporg-learn/workshop-details' ) ); ?>

E_NOTICE: Undefined index: attrs in wp-includes/block-supports/elements.php:20

How has this been tested?

• Visual testing

Screenshots

Types of changes

Bug fix

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[dd32]

To note, I questioned if the $parsed_block should just have the attrs field set, but it seems like checking for existence is done elsewhere already:

https://github.com/WordPress/wordpress-develop/blob/master/src/wp-includes/class-wp-block.php#L167-L170

[aristath]

I see no problem with adding an extra check here to avoid issues 👍

[youknowriad]

Looks like there's a unit test failure here.

[oandregal]

It seems the error is due to the WP_Block_Template class being present both in the WordPress environment (latest master from wordpress-develop) and the Gutenberg plugin. I can repro locally.

[oandregal]

@dd32 this needs to be rebased from trunk.

[oandregal]

I rebased this PR based on these instructions.