Offline participation: already submitted page

app/controllers/contests_controller.rb

@@ -124,6 +124,10 @@ class ContestsController < ApplicationController
     if !@offline
       not_found and return
     end
+
+    if @offline.images.length > 1
+      render :offline_already_submitted and return
+    end
   end
 
   def offline_update

app/views/contests/offline_already_submitted.html.slim

@@ -0,0 +1,2 @@
+.mt-3
+  = t("offlines.form.already_submitted")