Just a little failure with WP5 and PHP73

Hi!
I’m trying to apply this to a PhD project about Blended Learning, and I have a failure that I believe it’s not a complicated one. Could you help me? I’m trying to connect the WP with Learning Locker v2. All works fine, but when I run the queue I get the failure in the WP logs, which says:
——-
PHP Warning: Illegal string offset ‘version’ in /var/www/lab/wp-content/plugins/wp-experience-api/wp-experience-api-queue-obj.php on line 143
——-
That line I believe create the JSON information to send it. It’s this:
——-
$statement = serialize( $this->statement->asVersion( $this->lrs_info[ WP_Experience_Queue_Object::LRS_VERSION ] ) );
——-
At the beginning in the same file, LRS_VERSION is defined as…
——-
const LRS_VERSION = ‘version’;
——-

I’m don’t know much about PHP… Could you help me? Thanks!

The page I need help with: [log in to see the link]