Cannot open history sidebar in private browsing window

Noticed in my dev build. Steps to reproduce:

1. Open the browser with the default history settings.
2. Press Ctrl+H.
3. Press Ctrl+B, and try switching the sidebar to "History".

Expect: after step 2, the "History" sidebar should open.

Actual: after step 2, nothing happens. After step 3, nothing happens.

NOTE: In private browsing a user can still technically have history items if the browser previously had a non-private browsing window.