Nav block renderer error with markup for inner blocks

[getdave]

Raising a complimentary Issue in Gutenberg repo for https://core.trac.wordpress.org/ticket/60762.

What follows is pasted from that Trac ticket:

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class-wp-html-tag-processor.php on line 876 can have an null value passed to strlen() as $this->html resulting in a PHP8 error.
This seems to have originated from a change in WordPress/wordpress-develop@1f8bb9f#diff-1bea3165bce53d53ac51db1b623291fcd75ca59e08ec124df652312329160685L143-R169 where static::get_markup_for_inner_block( $inner_block ) can return null instead of an empty string.

If the function is changed from

private static function get_markup_for_inner_block( $inner_block ) {
	$inner_block_content = $inner_block->render();
	if ( ! empty( $inner_block_content ) ) {
		if ( static::does_block_need_a_list_item_wrapper( $inner_block ) ) {
			return '<li class="wp-block-navigation-item">' . $inner_block_content . '</li>';
		}
		return $inner_block_content;
	}
}

to the following, this is mitigated.

private static function get_markup_for_inner_block( $inner_block ) {
	$inner_block_content = $inner_block->render();
	if ( ! empty( $inner_block_content ) ) {
		if ( static::does_block_need_a_list_item_wrapper( $inner_block ) ) {
			return '<li class="wp-block-navigation-item">' . $inner_block_content . '</li>';
		}
	} else {
		$inner_block_content = '';
	}

	return $inner_block_content;
}