Added error status to download if it cant find the link

Signed-off-by: Israel Barreto Sant'Anna <ibsa14@inf.ufpr.br>

app/controllers/concerns/downloadable_controller.rb

@@ -4,7 +4,12 @@ module DownloadableController
   # GET /learning_objects/1/download
   def download
     downloadable.download(current_user, request.remote_ip)
-    redirect_to downloadable.download_link
+    link = downloadable.download_link
+    if !link.blank?
+      redirect_to link
+    else
+      render status: :internal_server_error
+    end
   end
 
   protected