### CI Link

https://gradle-enterprise.elastic.co/s/sa7kgcpbjsuyo

### Repro line

./gradlew ':x-pack:plugin:esql:internalClusterTest' --tests "org.elasticsearch.xpack.esql.action.EsqlActionTaskIT.testCancelRead" -Dtests.seed=A10FD59C7183AD95 -Dbuild.snapshot=false -Dtests.jvm.argline="-Dbuild.snapshot=false" -Dtests.locale=ga-IE -Dtests.timezone=Europe/Stockholm -Druntime.java=20

### Does it reproduce?

No

### Applicable branches

main

### Failure history

_No response_

### Failure excerpt

```
org.elasticsearch.xpack.esql.action.EsqlActionTaskIT > testCancelRead FAILED
    java.lang.AssertionError: 
    Expected: a collection with size <2>
         but: collection size was <0>
        at __randomizedtesting.SeedInfo.seed([A10FD59C7183AD95:34226718C99014F4]:0)
        at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:18)
        at org.junit.Assert.assertThat(Assert.java:956)
        at org.junit.Assert.assertThat(Assert.java:923)
        at org.elasticsearch.xpack.esql.action.EsqlActionTaskIT.lambda$getTasksStarting$2(EsqlActionTaskIT.java:229)
        at org.elasticsearch.test.ESTestCase.assertBusy(ESTestCase.java:1196)
        at org.elasticsearch.test.ESTestCase.assertBusy(ESTestCase.java:1169)
        at org.elasticsearch.xpack.esql.action.EsqlActionTaskIT.getTasksStarting(EsqlActionTaskIT.java:221)
        at org.elasticsearch.xpack.esql.action.EsqlActionTaskIT.testCancelRead(EsqlActionTaskIT.java:167)
```
x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/lucene/LuceneOperator.java
public static final NamedWriteableRegistry.Entry ENTRY = new NamedWriteableRegistry.Entry(
            Operator.Status.class,
            "lucene_source",
            Status::new
        );
        private final int processedSlices;
        private final int totalSlices;
        private final int pagesEmitted;
        private final int slicePosition;
        private final int sliceSize;
        private Status(LuceneOperator operator) {
            processedSlices = operator.processSlices;
            totalSlices = operator.sliceQueue.totalSlices();
            LuceneSlice slice = operator.currentSlice;
            final PartialLeafReaderContext leaf;
            int sliceIndex = operator.sliceIndex;
            if (slice != null && sliceIndex < slice.numLeaves()) {
                leaf = slice.getLeaf(sliceIndex);
            } else {
                leaf = null;