Compare compares with Previously published instead of Published

Description

Steps to reproduce:

1. Create new standard page.
2. Publish.
3. Edit page and publish.
4. Click Compare. (You are comparing the Published version with the Previously published version.) Note: This step is important, without it, you cannot reproduce the bug.
5. Close Compare view.
6. Edit page so you will now have three versions; one Previously published, one Published and one Draft version.
7. Click Compare.

Expected result: You compare your Draft with the Published version.

Actual result: You compare your Draft with the latest Previously Published version.