fix: only append if not empty

Author: vknabel

internal/controller/metalstackmachine_controller.go

@@ -450,7 +450,9 @@ func (r *machineReconciler) machineTags() []string {
 func (r *machineReconciler) additionalMachineTags(partition *models.V1PartitionResponse) []string {
 	tags := []string{
 		tag.New(corev1.LabelTopologyZone, r.infraCluster.Spec.Partition),
-		tag.New(corev1.LabelTopologyRegion, partition.Labels[tag.PartitionRegion]),
+	}
+	if partition.Labels != nil && partition.Labels[tag.PartitionRegion] != "" {
+		tags = append(tags, partition.Labels[tag.PartitionRegion])
 	}
 
 	return tags