The test failed with

```
org.elasticsearch.client.ResponseException: method [GET], host [http://[::1]:42877], URI [_xpack/usage], status line [HTTP/1.1 500 Internal Server Error]	
{"error":{"root_cause":[{"type":"null_pointer_exception","reason":"Cannot invoke \"org.elasticsearch.cluster.routing.ShardRouting.state()\" because the return value of \"org.elasticsearch.cluster.routing.RoutingNode.getByShardId(org.elasticsearch.index.shard.ShardId)\" is null"}],"type":"null_pointer_exception","reason":"Cannot invoke \"org.elasticsearch.cluster.routing.ShardRouting.state()\" because the return value of \"org.elasticsearch.cluster.routing.RoutingNode.getByShardId(org.elasticsearch.index.shard.ShardId)\" is null"},"status":500}	
	at __randomizedtesting.SeedInfo.seed([28FB9E766A1CE048:945C02A2D66038C1]:0)	
	at org.elasticsearch.client.RestClient.convertResponse(RestClient.java:347)	
	at org.elasticsearch.client.RestClient.performRequest(RestClient.java:313)	
	at org.elasticsearch.client.RestClient.performRequest(RestClient.java:288)	
	at org.elasticsearch.xpack.transform.integration.TransformUsageIT.testUsage(TransformUsageIT.java:37)	
[...]
```

**Build scan:**
https://gradle-enterprise.elastic.co/s/tcqj3z4gyxjgc/tests/:x-pack:plugin:transform:qa:single-node-tests:javaRestTest/org.elasticsearch.xpack.transform.integration.TransformUsageIT/testUsage

**Reproduction line:**
```
./gradlew ':x-pack:plugin:transform:qa:single-node-tests:javaRestTest' --tests "org.elasticsearch.xpack.transform.integration.TransformUsageIT.testUsage" -Dtests.seed=28FB9E766A1CE048 -Dtests.locale=ja -Dtests.timezone=Europe/Rome -Druntime.java=20
```

**Applicable branches:**
main

**Reproduces locally?:**
No

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.xpack.transform.integration.TransformUsageIT&tests.test=testUsage

**Failure excerpt:**
```
org.elasticsearch.client.ResponseException: method [GET], host [http://[::1]:42877], URI [_xpack/usage], status line [HTTP/1.1 500 Internal Server Error]
{"error":{"root_cause":[{"type":"null_pointer_exception","reason":"Cannot invoke \"org.elasticsearch.cluster.routing.ShardRouting.state()\" because the return value of \"org.elasticsearch.cluster.routing.RoutingNode.getByShardId(org.elasticsearch.index.shard.ShardId)\" is null"}],"type":"null_pointer_exception","reason":"Cannot invoke \"org.elasticsearch.cluster.routing.ShardRouting.state()\" because the return value of \"org.elasticsearch.cluster.routing.RoutingNode.getByShardId(org.elasticsearch.index.shard.ShardId)\" is null"},"status":500}

  at __randomizedtesting.SeedInfo.seed([28FB9E766A1CE048:945C02A2D66038C1]:0)
  at org.elasticsearch.client.RestClient.convertResponse(RestClient.java:347)
  at org.elasticsearch.client.RestClient.performRequest(RestClient.java:313)
  at org.elasticsearch.client.RestClient.performRequest(RestClient.java:288)
  at org.elasticsearch.xpack.transform.integration.TransformUsageIT.testUsage(TransformUsageIT.java:37)
  at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
  at java.lang.reflect.Method.invoke(Method.java:578)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.invoke(RandomizedRunner.java:1758)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$8.evaluate(RandomizedRunner.java:946)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$9.evaluate(RandomizedRunner.java:982)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$10.evaluate(RandomizedRunner.java:996)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleSetupTeardownChained$1.evaluate(TestRuleSetupTeardownChained.java:48)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.tests.util.TestRuleThreadAndTestName$1.evaluate(TestRuleThreadAndTestName.java:45)
  at org.apache.lucene.tests.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.tests.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:390)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.forkTimeoutingTask(ThreadLeakControl.java:843)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$3.evaluate(ThreadLeakControl.java:490)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.runSingleTest(RandomizedRunner.java:955)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$5.evaluate(RandomizedRunner.java:840)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$6.evaluate(RandomizedRunner.java:891)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$7.evaluate(RandomizedRunner.java:902)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleStoreClassName$1.evaluate(TestRuleStoreClassName.java:38)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleAssertionsRequired$1.evaluate(TestRuleAssertionsRequired.java:53)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.tests.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at org.apache.lucene.tests.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.tests.util.TestRuleIgnoreTestSuites$1.evaluate(TestRuleIgnoreTestSuites.java:47)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:390)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.lambda$forkTimeoutingTask$0(ThreadLeakControl.java:850)
  at java.lang.Thread.run(Thread.java:1623)

```
x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/DataTiersUsageTransportAction.java
static Map<String, DataTiersFeatureSetUsage.TierSpecificStats> calculateStats(
        List<NodeStats> nodesStats,
        Map<String, String> indexByTier,
        RoutingNodes routingNodes
    ) {
        Map<String, TierStatsAccumulator> statsAccumulators = new HashMap<>();
        for (NodeStats nodeStats : nodesStats) {
            aggregateDataTierNodeCounts(nodeStats, statsAccumulators);
            aggregateDataTierIndexStats(nodeStats, routingNodes, indexByTier, statsAccumulators);
        }
        Map<String, DataTiersFeatureSetUsage.TierSpecificStats> results = new HashMap<>();
        for (Map.Entry<String, TierStatsAccumulator> entry : statsAccumulators.entrySet()) {
            results.put(entry.getKey(), calculateFinalTierStats(entry.getValue()));
        }
        return results;
    }
    /**
     * Determine which data tiers this node belongs to (if any), and increment the node counts for those tiers.
     */
    private static void aggregateDataTierNodeCounts(NodeStats nodeStats, Map<String, TierStatsAccumulator> tiersStats) {
        nodeStats.getNode()
            .getRoles()
            .stream()
            .map(DiscoveryNodeRole::roleName)
            .filter(DataTier::validTierName)
            .forEach(tier -> tiersStats.computeIfAbsent(tier, k -> new TierStatsAccumulator()).nodeCount++);
    }
    /**
     * Locate which indices are hosted on the node specified by the NodeStats, then group and aggregate the available index stats by tier.