Fix pagination attributes not being returned in ungroupable-only pages (#30688)

app/serializers/rest/notification_group_serializer.rb

@@ -45,6 +45,6 @@ class REST::NotificationGroupSerializer < ActiveModel::Serializer
   end
 
   def paginated?
-    instance_options[:group_metadata].present?
+    !instance_options[:group_metadata].nil?
   end
 end

spec/requests/api/v2_alpha/notifications_spec.rb

@@ -58,6 +58,7 @@ RSpec.describe 'Notifications' do
 
         expect(response).to have_http_status(200)
         expect(body_json_types.uniq).to eq ['mention']
+        expect(body_as_json[0][:page_min_id]).to_not be_nil
       end
     end