Redirect to the memberlist if the user enters an valid existing session
Fixes #188 (closed)
The redirect logic is now: -> The user clicks on the session name in the splashscreen: Redirect to memberlist if it is valid -> The user enters the session name and clicks on "edit": Redirect to memberlist if it is valid -> The user navigates to /hashtagmanagement and clicks on the session name or the edit button: Route to /question