Fix current_send_in_progress metric always being zero (#18160)

cmd/metrics-v2.go

@@ -2556,8 +2556,10 @@ func getNotificationMetrics() *MetricsGroup {
 		cacheInterval: 10 * time.Second,
 	}
 	mg.RegisterRead(func(ctx context.Context) []Metric {
-		nstats := globalNotifyTargetList.Stats()
-		metrics := make([]Metric, 0, 1+len(nstats.TargetStats))
+		metrics := make([]Metric, 0, 3)
+
+		if globalEventNotifier != nil {
+			nstats := globalEventNotifier.targetList.Stats()
 			metrics = append(metrics, Metric{
 				Description: MetricDescription{
 					Namespace: minioNamespace,
@@ -2581,6 +2583,7 @@ func getNotificationMetrics() *MetricsGroup {
 					Value:          float64(st.CurrentQueue),
 				})
 			}
+		}
 
 		lstats := globalLambdaTargetList.Stats()
 		for _, st := range lstats.TargetStats {