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 WordPress/gutenberg#63436.

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

Fixes #61656.
Props andrewserong, mukesh27, aaronrobertshaw.

git-svn-id: https://develop.svn.wordpress.org/branches/6.6@58761 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/block-supports/layout.php

@@ -322,14 +322,22 @@ function wp_get_layout_style( $selector, $layout, $has_block_gap_support = false
 			 * They're added separately because padding might only be set on one side.
 			 */
 			if ( isset( $block_spacing_values['declarations']['padding-right'] ) ) {
-				$padding_right   = $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)" ),
 				);
 			}
 			if ( isset( $block_spacing_values['declarations']['padding-left'] ) ) {
-				$padding_left    = $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)" ),