Do not save invalid disconnect time

core/stats.go

@@ -136,9 +136,11 @@ func saveStats() error {
 	if err := data.SetPeakSessionViewerCount(_stats.SessionMaxViewerCount); err != nil {
 		log.Errorln("error saving viewer count", err)
 	}
+	if _stats.LastDisconnectTime.Valid {
 		if err := data.SetLastDisconnectTime(_stats.LastConnectTime.Time); err != nil {
 			log.Errorln("error saving disconnect time", err)
 		}
+	}
 
 	return nil
 }