How do I disable the menu for mobile?

I’m using the Cronus template to build a simple single-page site. I don’t need a menu. I’ve deleted all menus, and the Header Menu is “unassigned.” As planned, the menu does not appear on my laptop browser, but when the window is narrowed or when the site is loaded on my iPhone, the menu icon appears in the upper right. It’s distracting, it’s empty, and it opens an ugly purple search field. How can I get rid of it? Any ideas would be appreciated.

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