Block Themes: Fix invalid css for nested fullwidth layouts with zero padding applied

In the Layout block support, handle 0 values for padding as 0px in calc() rules. This resolves a bug for nested fullwidth layouts when zero padding is applied. Due to how calc() works, without supplying the unit, the rule will not
work, resulting in a horizontal scrollbar.

Ref: PHP changes from https://github.com/WordPress/gutenberg/pull/63436.

Reviewed by hellofromTonya.
Merges [58750]  to the 6.6 branch.

Fixes #61656.
Props andrewserong, mukesh27, aaronrobertshaw.
Built from https://develop.svn.wordpress.org/branches/6.6@58761


git-svn-id: http://core.svn.wordpress.org/branches/6.6@58163 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/block-supports/layout.php

@@ -323,6 +323,10 @@ function wp_get_layout_style( $selector, $layout, $has_block_gap_support = false
 			 */
 			if ( isset( $block_spacing_values['declarations']['padding-right'] ) ) {
 				$padding_right = $block_spacing_values['declarations']['padding-right'];
+				// Add unit if 0.
+				if ( '0' === $padding_right ) {
+					$padding_right = '0px';
+				}
 				$layout_styles[] = array(
 					'selector'     => "$selector > .alignfull",
 					'declarations' => array( 'margin-right' => "calc($padding_right * -1)" ),
@@ -330,6 +334,10 @@ function wp_get_layout_style( $selector, $layout, $has_block_gap_support = false
 			}
 			if ( isset( $block_spacing_values['declarations']['padding-left'] ) ) {
 				$padding_left = $block_spacing_values['declarations']['padding-left'];
+				// Add unit if 0.
+				if ( '0' === $padding_left ) {
+					$padding_left = '0px';
+				}
 				$layout_styles[] = array(
 					'selector'     => "$selector > .alignfull",
 					'declarations' => array( 'margin-left' => "calc($padding_left * -1)" ),

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.6.1-alpha-58760';
+$wp_version = '6.6.1-alpha-58761';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.