Fix error when terms of service are missing an effective date (#34200)

app/serializers/rest/terms_of_service_serializer.rb

@@ -4,7 +4,7 @@ class REST::TermsOfServiceSerializer < ActiveModel::Serializer
   attributes :effective_date, :effective, :content, :succeeded_by
 
   def effective_date
-    object.effective_date.iso8601
+    (object.effective_date || object.published_at).iso8601
   end
 
   def effective

app/views/admin/terms_of_service/index.html.haml

@@ -11,7 +11,7 @@
       .dot-indicator.success
         .dot-indicator__indicator
         %span
-          - if @terms_of_service.effective?
+          - if @terms_of_service.effective? || @terms_of_service.effective_date.nil?
             = t('admin.terms_of_service.live')
           - else
             = t('admin.terms_of_service.going_live_on_html', date: tag.time(l(@terms_of_service.effective_date), class: 'formatted', date: @terms_of_service.effective_date.iso8601))