==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.6.2 PGSQL edition
- Deployed with iRedMail Easy or the downloadable installer? Downloadable
- Linux/BSD distribution name and version: Ubuntu Ubuntu 22.04.2 LTS
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): PGSQL
- Web server (Apache or Nginx):Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====
After updating the iRedAdmin according to the instructions(Migrate or upgrade iRedAdmin / iRedAdmin-Pro), the iRedAdmin stopped opening. It keeps reporting an error internal server error.
The logs contain the following entries

GET h ttps://mail.mydomain/iredadmin/

Traceback (most recent call last):
  File "/opt/www/iRedAdmin-2.7/web/application.py", line 274, in process
    return p(lambda: process(processors))
  File "/opt/www/iRedAdmin-2.7/web/session.py", line 91, in _processor
    self._cleanup()
  File "/opt/www/iRedAdmin-2.7/web/session.py", line 192, in _cleanup
    self.store.cleanup(timeout)
  File "/opt/www/iRedAdmin-2.7/web/session.py", line 368, in cleanup
    self.db.delete(self.table, where="$last_allowed_time > atime", vars=locals())
AttributeError: 'NoneType' object has no attribute 'delete'