#382 Logging in when viewing booking details breaks prev link

[Hedgehogs From Pluto]

At the following URL (or similar)
/mrbs/web/view_entry.php?id=22438&area=1&day=7&month=2&year=2017
Login or logout (i.e. if you're logged in then logout, if you're logged out, then login).

Then click the link 'Return to previous page'. You will notice that it takes you to the wrong page, i.e. it doesn't take you to the previous page.