Sliding Menu from "Learning React"

I am getting the following error message when I run npm start to test the slidingmenu. Please advise.
Line 16: The href attribute requires a valid value to be accessible. Provide a valid, navigable address as the href value. If you cannot provide a valid href, but still need the element to resemble a link, use a button and change it with appropriate styles. Learn more: jsx-a11y/anchor-is-valid

I am testing on a computer running Unbuntu 18.04 OS.
I appreciate your feedback.
Thank you,

This seems like a new change in behavior, though a good one from an accessibility point of view. The links currently just say “#” for the href attribute value. Replace that with any valid URL like foo.html, and this error should go away. Can you please try that and let me know?