Fix subscription seats update

Skip those without namespace and report to sentry

changelogs/unreleased/249040-fix-subscription-without-namespace.yml

+---
+title: Fix max seats used not updated in billing summary
+merge_request: 42184
+author:
+type: fixed

ee/app/workers/update_max_seats_used_for_gitlab_com_subscriptions_worker.rb

@@ -16,6 +16,11 @@ class UpdateMaxSeatsUsedForGitlabComSubscriptionsWorker # rubocop:disable Scalab
       tuples = []
 
       subscriptions.each do |subscription|
+        unless subscription.namespace
+          track_error(subscription)
+          next
+        end
+
         subscription.refresh_seat_attributes!
 
         tuples << [subscription.id, subscription.max_seats_used, subscription.seats_in_use, subscription.seats_owed]
@@ -33,4 +38,14 @@ class UpdateMaxSeatsUsedForGitlabComSubscriptionsWorker # rubocop:disable Scalab
       end
     end
   end
+
+  private
+
+  def track_error(subscription)
+    Gitlab::ErrorTracking.track_exception(
+      StandardError.new('Namespace absent'),
+      gitlab_subscription_id: subscription.id,
+      namespace_id: subscription.namespace_id
+    )
+  end
 end

ee/spec/workers/update_max_seats_used_for_gitlab_com_subscriptions_worker_spec.rb

@@ -103,6 +103,28 @@ RSpec.describe UpdateMaxSeatsUsedForGitlabComSubscriptionsWorker do
           .and change(gitlab_subscription_2, :seats_in_use).from(0).to(13)
           .and change(gitlab_subscription_2, :seats_owed).from(0).to(12)
       end
+
+      context 'when namespace is absent' do
+        before do
+          gitlab_subscription.update!(namespace_id: nil)
+        end
+
+        it 'skips the subscription' do
+          expect(Gitlab::ErrorTracking).to receive(:track_exception).with(
+            an_instance_of(StandardError),
+            { gitlab_subscription_id: gitlab_subscription.id, namespace_id: nil }
+          )
+
+          expect do
+            perform_and_reload
+          end.to not_change(gitlab_subscription, :max_seats_used).from(0)
+            .and not_change(gitlab_subscription, :seats_in_use).from(0)
+            .and not_change(gitlab_subscription, :seats_owed).from(0)
+            .and change(gitlab_subscription_2, :max_seats_used).from(0).to(14)
+            .and change(gitlab_subscription_2, :seats_in_use).from(0).to(13)
+            .and change(gitlab_subscription_2, :seats_owed).from(0).to(12)
+        end
+      end
     end
   end
 end