YARN-10647. Fix TestRMNodeLabelsManager failed after YARN-10501. Contributed by

Qi Zhu.

(cherry picked from commit 47420ae3edb9076d3aac7775de8712a7685dc135)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/nodelabels/CommonNodeLabelsManager.java

@@ -645,7 +645,9 @@ public class CommonNodeLabelsManager extends AbstractService {
           host.labels.addAll(labels);
           for (Node node : host.nms.values()) {
             replaceNodeForLabels(node.nodeId, node.labels, labels);
-            replaceLabelsForNode(node.nodeId, node.labels, labels);
+            if (node.labels != null && labels != null) {
+              replaceLabelsForNode(node.nodeId, node.labels, labels);
+            }
             node.labels = null;
           }
           break;