Custom order status Php 8.0 warning

I was using below code to have custom order status with php 7.4 My host will end php 7.4 support thus I have to use php 8.0.

I got "Attempt to read property "ID" on null" warning for this line.

How I can fix it?

    if( get_post_type($post->ID) != 'shop_order' ) return; // Exit

    //Packed Status
function register_packed_order_status() {
    register_post_status( 'wc-packed', array(
        'label'                     => 'Packed',
        'public'                    => true,
        'show_in_admin_status_list' => true,
        'show_in_admin_all_list'    => true,
        'exclude_from_search'       => false,
        'label_count'               => _n_noop( 'Packed <span class="count">(%s)</span>', 'Packed <span class="count">(%s)</span>' )
    ) );
}
add_action( 'init', 'register_packed_order_status' );

function add_packed_to_order_statuses( $order_statuses ) {
    $new_order_statuses = array();
    foreach ( $order_statuses as $key => $status ) {
        $new_order_statuses[ $key ] = $status;
        if ( 'wc-processing' === $key ) {
            $new_order_statuses['wc-packed'] = 'Packed';
        }
    }
    return $new_order_statuses;
}
add_filter( 'wc_order_statuses', 'add_packed_to_order_statuses' );
// 3. ADD COLOR TO IN PROGRESS BUTTON
add_action('admin_head', 'styling_packed_order_list' );
function styling_packed_order_list() {
    global $pagenow, $post;

    if( $pagenow != 'edit.php') return; // Exit
    if( get_post_type($post->ID) != 'shop_order' ) return; // Exit

    // HERE below set your custom status
    $order_status = 'packed'; // <==== HERE
    ?>
    <style>
        .order-status.status-<?php echo sanitize_title( $order_status ); ?> {
            background: #0D98BA;
            color: #ffffff;
        }
    </style>
    <?php
}