I'm seeing quite a few of these in prod:

```
java.lang.NullPointerException: Cannot invoke "org.elasticsearch.xpack.core.transform.transforms.TransformState.getTaskState()" because "transformState" is null
    at org.elasticsearch.xpack.transform.TransformUsageTransportAction.masterOperation(TransformUsageTransportAction.java:106) ~[?:?]
    at org.elasticsearch.xpack.transform.TransformUsageTransportAction.masterOperation(TransformUsageTransportAction.java:55) ~[?:?]
    at org.elasticsearch.action.support.master.TransportMasterNodeAction.executeMasterOperation(TransportMasterNodeAction.java:124) ~[elasticsearch-8.9.0.jar:?]
    at org.elasticsearch.action.support.master.TransportMasterNodeAction$AsyncSingleAction.lambda$doStart$3(TransportMasterNodeAction.java:235) ~[elasticsearch-8.9.0.jar:?]
    at org.elasticsearch.action.ActionRunnable$3.doRun(ActionRunnable.java:72) ~[elasticsearch-8.9.0.jar:?]
    at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:983) ~[elasticsearch-8.9.0.jar:?]
    at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26) ~[elasticsearch-8.9.0.jar:?]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) ~[?:?]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) ~[?:?]
    at java.lang.Thread.run(Thread.java:1623) ~[?:?]
```

`org.elasticsearch.persistent.PersistentTasksCustomMetadata.PersistentTask#getState` is declared `@Nullable` but this case is not handled properly by the usage action.
x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/action/TransportGetDataFrameAnalyticsStatsAction.java
DataFrameAnalyticsTask,
    GetDataFrameAnalyticsStatsAction.Request,
    GetDataFrameAnalyticsStatsAction.Response,
    QueryPage<Stats>> {
    private static final Logger logger = LogManager.getLogger(TransportGetDataFrameAnalyticsStatsAction.class);
    private final Client client;
    @Inject
    public TransportGetDataFrameAnalyticsStatsAction(
        TransportService transportService,
        ClusterService clusterService,
        Client client,
        ActionFilters actionFilters
    ) {
        super(
            GetDataFrameAnalyticsStatsAction.NAME,
            clusterService,
            transportService,
            actionFilters,
            GetDataFrameAnalyticsStatsAction.Request::new,
            GetDataFrameAnalyticsStatsAction.Response::new,
            in -> new QueryPage<>(in, GetDataFrameAnalyticsStatsAction.Response.Stats::new),
            transportService.getThreadPool().executor(ThreadPool.Names.MANAGEMENT)
        );
        this.client = client;
    }