Don't run preg_match() on null values

[dd32]

PHP 8.1 has deprecated passing null as the second parameter to preg_match(), generating the following Deprecated notice: preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated.

What?

Avoids a PHP Deprecated notice

Why?

PHP 8.1 has deprecated passing null values to preg_match(), which is the default condition here.

How?

Check the $block_gap is a non-falsey value before processing it.
This style is already used for this variable value further down the stack:

gutenberg/lib/block-supports/layout.php

Line 73 in 6de1698

$gap_style = $gap_value && ! $should_skip_gap_serialization ? $gap_value : 'var( --wp--style--block-gap )';

The changes in this PR could also be written as:

-		$gap_value = $gap_value && preg_match( '%[\\\(&=}]|/\*%', $gap_value ) ? null : $gap_value;
+		$gap_value = ! $gap_value || preg_match( '%[\\\(&=}]|/\*%', $gap_value ) ? null : $gap_value;

both are logically the same here (although different around a 0 or false, which is not supported here due to the above mentioned code), as it's only checking to see if it contains invalid characters.

Testing Instructions

Unknown.

Have a block that does not contain the blockGap key: _wp_array_get( $block, array( 'attrs', 'style', 'spacing', 'blockGap' ) ).

Screenshots or screencast

[aristath]

LGTM! 👍

[aristath]

The failing e2e test here is unrelated to this PR, and this is an essential fix for PHP8.x compatibility so I'll go ahead and merge this.
The code looks good, makes perfect sense, and works as expected.

[ramonjd]

Thanks for catching that!