Attempt to read property “ID” on null in sitewide-tags.php on line 421

I run WordPress v6.5.5 as a MultiSite. I use PHP 8.2.20.
I have the WordPress MU Sitewide Tags Pages plug-in installed and it has served me well over the years.

However, since upgrading PHP, I encounter an error with this plug-in enabled. For instance, when I want to write a new blogpost on one of the member sites, I get the following error:

PHP Warning: Attempt to read property "ID" on null in F:\DirTeam.com\wwwroot\wp-content\plugins\wordpress-mu-sitewide-tags\sitewide-tags.php on line 421

When the plug-in is removed, this error does not occur, but I lose the functionality of the plug-in.

Line 421 and beyond read like this:

$global_post = $wpdb->get_row( $wpdb->prepare( "SELECT * FROM {$wpdb->posts} WHERE guid IN (%s,%s)", $post->guid, esc_url( $post->guid ) ) );
if( $post->post_status != 'publish' && is_object( $global_post ) ) {
    wp_delete_post( $global_post->ID );
} else {
    if( $global_post->ID != '' ) {
        $post->ID = $global_post->ID; // editing an old post

        foreach( array_keys( $global_meta ) as $key )
            delete_post_meta( $global_post->ID, $key );
    } else {
        unset( $post->ID ); // new post
    }
}
if( $post->post_status == 'publish' ) {
    $post->ping_status = 'closed';
    $post->comment_status = 'closed';

    /* Use the category ID in the post */
        $post->post_category = $category_id;

    $p = wp_insert_post( $post );
    foreach( $global_meta as $key => $value )
        if( $value )
            add_post_meta( $p, $key, $value );
}

How do I overcome this error?

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