Result of query for services is used before handling possible error (#…

…405)

* Result of query for services is used before handling possible error

* Return early when a non-replicated service is matched

cmd/backup/stop_restart.go

@@ -151,15 +151,21 @@ func (s *script) stopContainersAndServices() (func() error, error) {
 			}),
 			Status: true,
 		})
+		if err != nil {
+			return noop, errwrap.Wrap(err, "error querying for services to scale down")
+		}
 		for _, s := range matchingServices {
+			if s.Spec.Mode.Replicated == nil {
+				return noop, errwrap.Wrap(
+					nil,
+					fmt.Sprintf("only replicated services can be restarted, but found a label on service %s", s.Spec.Name),
+				)
+			}
 			servicesToScaleDown = append(servicesToScaleDown, handledSwarmService{
 				serviceID:           s.ID,
 				initialReplicaCount: *s.Spec.Mode.Replicated.Replicas,
 			})
 		}
-		if err != nil {
-			return noop, errwrap.Wrap(err, "error querying for services to scale down")
-		}
 	}
 
 	if len(containersToStop) == 0 && len(servicesToScaleDown) == 0 {