Make sure the Finish page can only be completed once.

anne-survey.rb

@@ -128,12 +128,12 @@ module Anne::Controllers
     def get
       return redirect Index if not @state["user"]
       return redirect Vote unless next_image.first.nil?
-      # FIXME: check whether email/prize/results have been sent, and redirect to Thanks.
+      return redirect Thanks unless @state["user"].results.nil?
       render :finish
     end
 
     def post
-      user = User.find(@state["user"].id)
+      user = @state["user"]
       raise "unknown user" if user.nil?
       user.email = @input.email
       user.prize = !@input.prize.nil?