Upgraded osTicket from 1.10.4 to 1.11, and PHP from 5.6 to 7.2. After upgrade, each time a user creates a ticket , PHP event is logged:
[06-Mar-2019 11:26:10 UTC] PHP Warning: session_regenerate_id(): Cannot regenerate session id - session is not active in C:\inetpub\osTicket\open.php on line 49
[06-Mar-2019 11:26:10 UTC] PHP Fatal error: Uncaught Error: Call to a member function getId() on null in C:\inetpub\osTicket\include\client\view.inc.php:140
#0 C:\inetpub\osTicket\tickets.php(147): include()
There are no "visible" issues for the user. Everything seems to work fine, but error is logged each time a ticket is created.
I also had errors as described in https://forum.osticket.com/d/90697-signing-out-fails-and-errors but after applying suggested solution, they were resolved.