k8s probe: Fix a panic (nil pointer deref) when a cronjob has never b…

…een scheduled

in which case cj.Status.LastScheduled is nil.
New behaviour is to omit it from the map (and therefore the display) if it has never been scheduled.

probe/kubernetes/cronjob.go

@@ -63,11 +63,14 @@ func (cj *cronJob) Selectors() ([]labels.Selector, error) {
 }
 
 func (cj *cronJob) GetNode() report.Node {
-	return cj.MetaNode(report.MakeCronJobNodeID(cj.UID())).WithLatests(map[string]string{
-		NodeType:      "CronJob",
-		Schedule:      cj.Spec.Schedule,
-		Suspended:     fmt.Sprint(cj.Spec.Suspend != nil && *cj.Spec.Suspend), // nil -> false
-		LastScheduled: cj.Status.LastScheduleTime.Format(time.RFC3339Nano),
-		ActiveJobs:    fmt.Sprint(len(cj.jobs)),
-	})
+	latest := map[string]string{
+		NodeType:   "CronJob",
+		Schedule:   cj.Spec.Schedule,
+		Suspended:  fmt.Sprint(cj.Spec.Suspend != nil && *cj.Spec.Suspend), // nil -> false
+		ActiveJobs: fmt.Sprint(len(cj.jobs)),
+	}
+	if cj.Status.LastScheduleTime != nil {
+		latest[LastScheduled] = cj.Status.LastScheduleTime.Format(time.RFC3339Nano)
+	}
+	return cj.MetaNode(report.MakeCronJobNodeID(cj.UID())).WithLatests(latest)
 }