Help whit compare

Hi, can you help me whit compare on my page?

When i don’t choose anything there is worning:
Warning: Division by zero in /strefa24/wp-content/plugins/fs-real-estate-plugin/includes/compare.php on line 16

What should I make and where to have an information: You didn’t coose anything. Try one more time on homepage.

https://www.ads-software.com/extend/plugins/fs-real-estate-plugin/