After upgrading OS. i faced problem with display.
i fixed some problem with
npm audit fix --force.
Then i shifted to VNC
used DISPLAY=:1 and then the magicmirror started.
but now there ware two process running at time.
MagicMirror with DISPLAY=:0
MM with DISPLAY=:1
so using pm2 i deleted MagicMirror and gave reboot.
everything worked perfectly. so i changed back DISPLAY=:0 in MM.
and gave reboot again…
and problem solved. no black screen no error :)