The document is deleted when it has only one version if a revision deletion action is triggered with a non-existing version

Steps to reproduce :

1. Create a new page
2. Open the History tab (there should be one version in history: 1.1)
3. Copy the URL of the Delete link
4. Add to the URL the following parameters : &rev1=2.1&rev2=2.1 (use any revision number that does not show up in history)
5. Access the new URL in the browser
6. Click on Yes when asking if Are you sure you wish to delete versions from 2.1 to 2.1 inclusive?

Expected result :

The page is not deleted, as the version used for deletion does not exist.

Actual result :

The page is deleted.