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
listener.onResponse(new QueryPage<>(Collections.emptyList(), 0, GetDataFrameAnalyticsAction.Response.RESULTS_FIELD));
                return;
            }
            Stats stats = buildStats(
                task.getParams().getId(),
                statsHolder.getProgressTracker().report(),
                statsHolder.getDataCountsTracker().report(),
                statsHolder.getMemoryUsage(),
                statsHolder.getAnalysisStats()
            );
            listener.onResponse(new QueryPage<>(Collections.singletonList(stats), 1, GetDataFrameAnalyticsAction.Response.RESULTS_FIELD));
        }, listener::onFailure);
        
        task.updateTaskProgress(updateProgressListener);
    }
    @Override
    protected void doExecute(
        Task task,
        GetDataFrameAnalyticsStatsAction.Request request,
        ActionListener<GetDataFrameAnalyticsStatsAction.Response> listener
    ) {
        TaskId parentTaskId = new TaskId(clusterService.localNode().getId(), task.getId());
        logger.trace("Get stats for data frame analytics [{}]", request.getId());
        ActionListener<GetDataFrameAnalyticsAction.Response> getResponseListener = ActionListener.wrap(getResponse -> {
            List<String> expandedIds = getResponse.getResources()
                .results()
                .stream()
                .map(DataFrameAnalyticsConfig::getId)
                .collect(Collectors.toList());