Details
Description
If you are viewing the admin page with an active contest (so that admin site is prefixed by the contest id in the URL) and you delete that contest, you get a 404 error afterwards instead of for example being taken into proper admin page without the contest prefix.
https://gerrit.sio2project.mimuw.edu.pl/3101
SIO-2045Page not found error after deleting a contestRedirect to contest-unprefixed url of contests list after calling delete_selected for contests
Change-Id: Ie1be299d45e883181c9e4f2ec0d80ca554685b59