Hi Ariba an Nagesh,
Today I was trying on a live website (php8.1 and Joomla! 3.10.11) currently using the template Arino, the Helix ultimate template. The reason is, to see if I am able to create the same looks with the Helix Ultimate as what I had done earlier with te (some older) Arino template in preparation for Joomla 4.
I also saw this same error when I tried to edit the Helix Ultimate template. This template uses "a sort of" frontpage editing to create the user preferences and looks.
Now the solution lies within the fact that it's a live website I was editing, and a while ago I had set page compression, JS compression an css compression, also compile css to scss. And the setting "yes" in the Joomla ->general settings->Production mode.
Maybe the problem Nagesh is experience will be gone if he first remove al the compression settings and check the production mode. and deleting the cache. I tried a couple of tests to get the error back, and solved again. I truly hope this will be also the solution for him. Best regards! Rob