fix runRepairer to check nil in order to avoid SEGV (#788)

Author: YZ775

sabakan/generator.go

@@ -18,6 +18,7 @@ var (
 	errNotAvailable       = errors.New("no healthy machine is available")
 	errMissingMachine     = errors.New("failed to apply new template due to missing machines")
 	errTooManyNonExistent = errors.New("too many non-existent control plane nodes")
+	errClusterNotFound    = errors.New("CKE cluster does not exist")
 
 	// DefaultWaitRetiredSeconds before removing retired nodes from the cluster.
 	DefaultWaitRetiredSeconds = 300.0

sabakan/integrate.go

@@ -156,6 +156,10 @@ func (ig integrator) runGenerator(ctx context.Context, leaderKey string, cluster
 func (ig integrator) runRepairer(ctx context.Context, clusterStatus *cke.ClusterStatus) error {
 	st := cke.Storage{Client: ig.etcd}
 
+	if clusterStatus == nil {
+		return errClusterNotFound
+	}
+
 	disabled, err := st.IsAutoRepairDisabled(ctx)
 	if err != nil {
 		return err