The navigation when previewing an empty survey (without a page) in the back-office should be improved:

• There is a "start" button
• When the "start" button is clicked, the end page appears with "previous" and "end" buttons, and with the "mandatory fields" hint (which does not appear on the end page when the survey is not empty)
• The "previous" button on the end page clears the end message and buttons: we're on an unknown state.

IMHO, either the start button should be removed, or the previous button should be removed from the end page.