Error in admin/dashboard: A non numeric value encountered..

“A non numeric value encountered in /home/xyz/public_html/wp-content/plugins/visualizer/classes/Visualizer/Module/Admin.php on line 219”
This error is regularly appearing in my admin dashboard area. It can appear during any activity such as simple post edits, updating a gravity form .. I am not doing anything visualizer related.
I am on php 7.1.24, siteground hosting, use Udesign by Andon theme 2.14.0, wordpress 4.9.8, apache, firefox browser, windows 10, visualizer version 3.1.1. The error appears briefly on an otherwise blank grey screen and then resides at the top of my admin / dashboard screen until move to another page. My website is https://gingerbeergolftravel.com/