For themes without theme.json file, make sure
to restore the inner div for the group block
to avoid breaking styles relying on that div.

function wp_restore_group_inner_container( $block_content, $block ) {
	$tag_name                         = isset( $block['attrs']['tagName'] ) ? $block['attrs']['tagName'] : 'div';
	$group_with_inner_container_regex = sprintf(
		'/(^s*]*wp-block-group(s|")[^>]*>)(s*]*wp-block-group__inner-container(s|")[^>]*>)((.|S|s)*)/U',
		preg_quote( $tag_name, '/' )
	);

	if (
		WP_Theme_JSON_Resolver::theme_has_support() ||
		1 === preg_match( $group_with_inner_container_regex, $block_content ) ||
		( isset( $block['attrs']['layout']['type'] ) && 'flex' === $block['attrs']['layout']['type'] )
	) {
		return $block_content;
	}

	$replace_regex   = sprintf(
		'/(^s*]*wp-block-group[^>]*>)(.*)(%1$s>s*$)/ms',
		preg_quote( $tag_name, '/' )
	);
	$updated_content = preg_replace_callback(
		$replace_regex,
		static function( $matches ) {
			return $matches[1] . '
' . $matches[2] . '
' . $matches[3];
		},
		$block_content
	);
	return $updated_content;
}