Default branch button shows on default branch in private repo #2306

At the main page of a private repo (personal free account):

https://github.com/<name>/<private-repo>

The master branch button is shown next to the branch selector, even though we are on the default branch (and have no other branches):

<img width="246" alt="Screen Shot 2019-08-05 at 3 38 07 PM" src="https://user-images.githubusercontent.com/3578574/62499319-131b1f00-b797-11e9-8da9-07f8a5c40e82.png">

I've tried clicking the button and reloading the page without change.

This bug does not occur on a public repo. I have my personal token in options.