### Elasticsearch Version

8.1.1

### Installed Plugins

_No response_

### Java Version

_bundled_

###  OS Version

Darwin Kernel Version 21.4.0

### Problem Description

Under certain conditions, executing a range enrich policy on a field with wrong datatype gives a NPE instead of a more comprehensible error.

### Steps to Reproduce

```
PUT enrich_index
{
  "mappings": {
    "properties": {
      "object": {
        "properties": {
          "field": {
            "type": "keyword"
          }
        }
      }
    }
  }
}

PUT /_enrich/policy/enrich_policy
{
  "range": {
    "indices": "enrich_index",
    "match_field": "object",
    "enrich_fields": ["enrich_field"]
  }
}

POST /_enrich/policy/enrich_policy/_execute
```

Executing the policy returns:
```json
{
  "error" : {
    "root_cause" : [
      {
        "type" : "null_pointer_exception",
        "reason" : "Cannot invoke \"String.hashCode()\" because \"<local7>\" is null"
      }
    ],
    "type" : "null_pointer_exception",
    "reason" : "Cannot invoke \"String.hashCode()\" because \"<local7>\" is null"
  },
  "status" : 500
}
```

Interestingly enough, if the enrich index were created like this (without subfield in `object`):
```
PUT enrich_index
{
  "mappings": {
    "properties": {
      "object": {
        "properties": {
        }
      }
    }
  }
}
```
 

Executing the policy would return a much better error:
```json
{
  "error" : {
    "root_cause" : [
      {
        "type" : "exception",
        "reason" : "Field 'object' has type [object] which doesn't appear to be a range type"
      }
    ],
    "type" : "exception",
    "reason" : "Field 'object' has type [object] which doesn't appear to be a range type"
  },
  "status" : 500
}
```



### Logs (if relevant)

_No response_
x-pack/plugin/enrich/src/main/java/org/elasticsearch/xpack/enrich/EnrichPolicyRunner.java
enrichOriginClient().admin()
            .indices()
            .refresh(
                new RefreshRequest(destinationIndexName),
                listener.delegateFailure((l, r) -> ensureSingleSegment(destinationIndexName, attempt))
            );
    }
    protected void ensureSingleSegment(final String destinationIndexName, final int attempt) {
        enrichOriginClient().admin()
            .indices()
            .segments(new IndicesSegmentsRequest(destinationIndexName), new ActionListener.Delegating<>(listener) {
                @Override
                public void onResponse(IndicesSegmentResponse indicesSegmentResponse) {
                    IndexSegments indexSegments = indicesSegmentResponse.getIndices().get(destinationIndexName);
                    if (indexSegments == null) {
                        throw new ElasticsearchException(
                            "Could not locate segment information for newly created index [{}]",
                            destinationIndexName
                        );
                    }
                    Map<Integer, IndexShardSegments> indexShards = indexSegments.getShards();
                    assert indexShards.size() == 1 : "Expected enrich index to contain only one shard";
                    ShardSegments[] shardSegments = indexShards.get(0).shards();
                    assert shardSegments.length == 1 : "Expected enrich index to contain no replicas at this point";
                    ShardSegments primarySegments = shardSegments[0];
                    if (primarySegments.getSegments().size() > 1) {
                        int nextAttempt = attempt + 1;
                        if (nextAttempt > maxForceMergeAttempts) {
                            delegate.onFailure(
                                new ElasticsearchException(