fix: return early in service reconciler when lb is nil

When buildModel returns lb == nil (e.g. for a ClusterIP service that
should not have a load balancer, such as one created by Istio Gateway
API with networking.istio.io/service-type: ClusterIP), the reconciler
correctly runs cleanupLoadBalancerResources but then falls through to
reconcileLoadBalancerResources with lb still nil. This causes a nil
pointer dereference panic at lb.DNSName().Resolve(ctx).

Add a return nil after successful cleanup when lb == nil so the
reconciler exits cleanly without entering the LB provisioning path.

Related: #4724

Signed-off-by: Joey Jonko <joey.jonko@happyreturns.com>

Author: joey-jonko-paypal

controllers/service/service_controller.go

@@ -137,6 +137,7 @@ func (r *serviceReconciler) reconcile(ctx context.Context, req reconcile.Request
 		if err != nil {
 			return ctrlerrors.NewErrorWithMetrics(controllerName, "cleanup_load_balancer_error", err, r.metricsCollector)
 		}
+		return nil
 	}
 	return r.reconcileLoadBalancerResources(ctx, svc, stack, lb, backendSGRequired)
 }