Error showing up

I have an error on my website that i need someone to sort out - this is a quick job ive been told but i don't know what im doing with it. The website is not live yet but in the stages of development still and id like this error to sort out.

The error is Warning: Trying to access array offset on value of type null in /homepages/31/d4296940345/htdocs/wordpress/wp-content/plugins/elementor/includes/base/controls-stack.php on line 1578


Please dont reply to me unless you can tell me what 4+4 =
i wont give you the work