Ivory Search stopped working

I use the Ivory Search plug-in on my website. It appears at the right end of my top menu. When you click on it, a drop-down should appear that allows the user to enter a search term. It has worked in the past, but now it just show a link to # in my domain. I’m not sure when it stopped working. I’ve contacted the author who determined that Bento generates a javascript error and suggested that I contact you. The problem occurs on Windows 10 with Chrome, Firefox and Edge. It does work on an Android mobile phone in both the Chrome browser and the Samsung Internet browser.

I do not see a way to include an image in this report so I can’t include a screenshot that Ivory Search author provided showing the error message. You should be able to reproduce it. The error message says:
Uncaught TypeError: Cannot read property ‘top’ of undefined
at HTMLAnchorElement.<anonymous> (theme-scripts.1s?ver?ver=5.5.1:323)
at HTMLAnchorElement.dispatch (jquery.1s?ver=1.12.4.wp:3)
at HTMLAnchorElement.r.handle (jquery.1s?ver=1.12.4.wp:3)

The page I need help with: [log in to see the link]