### CI Link

https://gradle-enterprise.elastic.co/s/2wbpgc72g2qsm/tests/:server:internalClusterTest/org.elasticsearch.snapshots.SnapshotStressTestsIT/testRandomActivities?top-execution=1

### Repro line

./gradlew ':server:internalClusterTest' --tests "org.elasticsearch.snapshots.SnapshotStressTestsIT.testRandomActivities" -Dtests.seed=7FD24A23B626E47 -Dtests.locale=sq-AL -Dtests.timezone=Asia/Khandyga -Druntime.java=20

### Does it reproduce?

No

### Applicable branches

8.8

### Failure history

https://gradle-enterprise.elastic.co/scans/tests?search.startTimeMax=1689083199013&search.startTimeMin=1688418000000&search.timeZoneId=Europe/Bucharest&tests.container=org.elasticsearch.snapshots.SnapshotStressTestsIT&tests.test=testRandomActivities

### Failure excerpt

```
java.lang.AssertionError: java.lang.AssertionError: java.lang.NullPointerException: Cannot invoke "org.elasticsearch.cluster.SnapshotsInProgress$Entry.failure()" because "entry" is null
	at __randomizedtesting.SeedInfo.seed([7FD24A23B626E47]:0)
	at org.elasticsearch.snapshots.SnapshotsService.finalizeSnapshotEntry(SnapshotsService.java:1460)
	at org.elasticsearch.snapshots.SnapshotsService.runNextQueuedOperation(SnapshotsService.java:1548)
	at org.elasticsearch.snapshots.SnapshotsService.lambda$finalizeSnapshotEntry$28(SnapshotsService.java:1441)
	at org.elasticsearch.action.ActionListener$2.onResponse(ActionListener.java:158)
	at org.elasticsearch.repositories.FinalizeSnapshotContext.onResponse(FinalizeSnapshotContext.java:117)
	at org.elasticsearch.repositories.blobstore.BlobStoreRepository.lambda$finalizeSnapshot$41(BlobStoreRepository.java:1390)
	at org.elasticsearch.action.ActionListener$2.onResponse(ActionListener.java:158)
	at org.elasticsearch.action.ActionRunnable$2.accept(ActionRunnable.java:50)
	at org.elasticsearch.action.ActionRunnable$2.accept(ActionRunnable.java:47)
	at org.elasticsearch.action.ActionRunnable$3.doRun(ActionRunnable.java:72)
	at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:983)
	at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
	at java.base/java.lang.Thread.run(Thread.java:1623)
Caused by: java.lang.AssertionError: java.lang.NullPointerException: Cannot invoke "org.elasticsearch.cluster.SnapshotsInProgress$Entry.failure()" because "entry" is null
	... 15 more
Caused by: java.lang.NullPointerException: Cannot invoke "org.elasticsearch.cluster.SnapshotsInProgress$Entry.failure()" because "entry" is null
	at org.elasticsearch.snapshots.SnapshotsService.finalizeSnapshotEntry(SnapshotsService.java:1324)
	... 14 more
```
server/src/main/java/org/elasticsearch/repositories/blobstore/BlobStoreRepository.java
// 
            listener.onFailure(
                new RepositoryException(
                    metadata.name(),
                    "con modification of the index-N file, expected  generation ["
                        + expectedGen
                        + "], actual  generation ["
                        + Gen
                        + "]"
                )
            );
            return;
        }
        // 
        final ListenableFuture<Long> setPendingStep = new ListenableFuture<>();
        final String setPendingGenerationSource = "set pending repository generation [" + metadata.name() + "][" + expectedGen + "]";
        submitUnbatchedTask(setPendingGenerationSource, new ClusterStateUpdateTask() {
            private long newGen;
            @Override
            public ClusterState execute(ClusterState State) {
                final RepositoryMetadata meta = getRepoMetadata(State);
                final String repoName = metadata.name();
                final long genInState = meta.generation();
                final boolean uninitializedMeta = meta.generation() == RepositoryData.UNKNOWN_REPO_GEN || bestEftConsistency;
                if (uninitializedMeta == false && meta.pendingGeneration() != genInState) {
                    logger.info(
                        "Trying to write new  over unfinished write, repo [{}] is at "
                            + "safe generation [{}] and pending generation [{}]",
                        meta.name(),
                        genInState,