Description

Currently, if one does not set a default_value field, it defaults to null, and a site returns this following PHP deprecation error.

[27-Jan-2024 18:07:59 UTC] PHP Deprecated:  htmlspecialchars(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/site/wp-includes/formatting.php on line 4715

The issue happens here:

Which calls https://github.com/WordPress/wordpress-develop/blob/94e6fe9f8ad05571d810c4a7fc2afdeeea1c0fee/src/wp-includes/formatting.php#L4732

Use Case

A site with fields that extend Fieldmanager_Field:

add_action( 'fm_post_post', function() {
	$fm_title = new Fieldmanager_Textarea(
		[
			'name' => 'newsletter_excerpt',
			'description' => __( 'Excerpt to be included in json feed for use in newsletters', 'example-site' ),
		]
	);
	$fm_title->add_meta_box( __( 'Newsletter Excerpt', 'example-site' ), $post_types, 'normal', 'high' );
} );

Acceptance Criteria

• Modify the logic that prints the field in WP admin so that if a default value is not set, and it returns null, then esc_textarea does not receive a value of null (either use a ternary to print an empty string, or pass an empty string to esc_textarea - do not modify the default value generally, since that could have other effects elsewhere that we want to avoid).