Fixed PHP 8.4 Deprecated Warnings

I’m not a PHP coder, but I got so tired of waiting for NextGen Gallery to fix the most basic of PHP 8.4 deprecations that I learnt and did it myself:

/wp-content/plugins/nextgen-gallery/src/DataMapper/Model.php on line 13

Change:

	public function __construct( \stdClass $object = null ) {

To:

	public function __construct(?\stdClass $object = null) {


/wp-content/plugins/nextgen-gallery/src/Display/View.php on line 108

Change:

	public function get_template_abspath( string $template = null ): string {

To:

	public function get_template_abspath(?string $template = null): string {