### Elasticsearch Version

7.16.2, master

### Installed Plugins

no

### Java Version

_bundled_

### OS Version

Linux iZbp1dn0ktfed9mjoyuiajZ 5.10.84-10.2.al8.x86_64 #1 SMP Thu Feb 10 15:03:09 CST 2022 x86_64 x86_64 x86_64 GNU/Linux

### Problem Description

When put repository using PutRespository API for an existing repository, NullPointerException was thrown, short stack shows as below
```
1> java.lang.Exception: java.lang.NullPointerException: Cannot invoke "org.elasticsearch.repositories.Repository.getMetadata()" because "repository" is null
  1>   at org.elasticsearch.cluster.service.MasterService.innerExecuteTasks(MasterService.java:916) ~[main/:?]
  1>   at org.elasticsearch.cluster.service.MasterService.executeTasks(MasterService.java:871) ~[main/:?]
  1>   at org.elasticsearch.cluster.service.MasterService.runTasks(MasterService.java:253) [main/:?]
  1>   at org.elasticsearch.cluster.service.MasterService$Batcher.run(MasterService.java:153) [main/:?]
  1>   at org.elasticsearch.cluster.service.TaskBatcher.runIfNotProcessed(TaskBatcher.java:114) [main/:?]
  1>   at org.elasticsearch.cluster.service.TaskBatcher$BatchedTask.run(TaskBatcher.java:170) [main/:?]
  1>   at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingRunnable.run(ThreadContext.java:714) [main/:?]
  1>   at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.runAndClean(PrioritizedEsThreadPoolExecutor.java:260) [main/:?]
  1>   at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.run(PrioritizedEsThreadPoolExecutor.java:223) [main/:?]
  1>   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136) [?:?]
  1>   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) [?:?]
  1>   at java.lang.Thread.run(Thread.java:833) [?:?]
```

### Steps to Reproduce

I've created an IT to reproduce this issue in [#85551](https://github.com/elastic/elasticsearch/pull/85551), steps can be described as following:
- put repository using `RestPutRepository` API and make sure non-master node failed to create repository.
- restart master let one of the previous non-master node become master
- put the same repository using the `RestPutRepository` API.

### Logs (if relevant)

_No response_
server/src/main/java/org/elasticsearch/repositories/RepositoriesService.java
private boolean found = false;
                private boolean changed = false;
                @Override
                public ClusterState execute(ClusterState currentState) {
                    Metadata metadata = currentState.metadata();
                    Metadata.Builder mdBuilder = Metadata.builder(currentState.metadata());
                    RepositoriesMetadata repositories = metadata.custom(RepositoriesMetadata.TYPE, RepositoriesMetadata.EMPTY);
                    List<RepositoryMetadata> repositoriesMetadata = new ArrayList<>(repositories.repositories().size() + 1);
                    for (RepositoryMetadata repositoryMetadata : repositories.repositories()) {
                        if (repositoryMetadata.name().equals(newRepositoryMetadata.name())) {
                            Repository existing = RepositoriesService.this.repositories.get(request.name());
                            if (existing == null) {
                                existing = RepositoriesService.this.internalRepositories.get(request.name());
                            }
                            assert existing != null : "repository [" + newRepositoryMetadata.name() + "] must exist";
                            assert existing.getMetadata() == repositoryMetadata;
                            final RepositoryMetadata updatedMetadata;
                            if (canUpdateInPlace(newRepositoryMetadata, existing)) {
                                if (repositoryMetadata.settings().equals(newRepositoryMetadata.settings())) {
                                    
                                    return currentState;
                                }
                                
                                updatedMetadata = repositoryMetadata.withSettings(newRepositoryMetadata.settings());
                            } else {
                                ensureRepositoryNotInUse(currentState, request.name());
                                updatedMetadata = newRepositoryMetadata;
                            }
                            found = true;
                            repositoriesMetadata.add(updatedMetadata);