Fix search for users with deleted consumer

app/views/external_users/index.html.slim

@@ -29,7 +29,7 @@ h1 = ExternalUser.model_name.human(count: 2)
       - @users.each do |user|
         tr
           td = link_to_if(policy(user).show?, user.displayname, user)
-          td = link_to_if(policy(user.consumer).show?, user.consumer, user.consumer)
+          td = link_to_if(user.consumer.present? && policy(user.consumer).show?, user.consumer, user.consumer)
           td = link_to(t('shared.show'), user) if policy(user).show?
 
 = render('shared/pagination', collection: @users)