### 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/test/java/org/elasticsearch/xpack/enrich/EnrichPolicyRunnerTests.java
listener.onFailure(e);
            }
        };
        return new EnrichPolicyRunner(
            policyName,
            policy,
            task,
            wrappedListener,
            clusterService,
            client,
            resolver,
            () -> createTime,
            randomIntBetween(1, 10000),
            randomIntBetween(1, 10)
        );
    }
    private ActionListener<ExecuteEnrichPolicyStatus> createTestListener(
        final CountDownLatch latch,
        final Consumer<Exception> exceptionConsumer
    ) {
        return new LatchedActionListener<>(ActionListener.wrap((r) -> logger.info("Run complete"), exceptionConsumer), latch);
    }
    private void validateMappingMetadata(Map<?, ?> mapping, String policyName, EnrichPolicy policy) {
        Object metadata = mapping.get("_meta");
        assertThat(metadata, is(notNullValue()));
        Map<?, ?> metadataMap = (Map<?, ?>) metadata;
        assertThat(metadataMap.get(EnrichPolicyRunner.ENRICH_README_FIELD_NAME), equalTo(EnrichPolicyRunner.ENRICH_INDEX_README_TEXT));
        assertThat(metadataMap.get(EnrichPolicyRunner.ENRICH_POLICY_NAME_FIELD_NAME), equalTo(policyName));
        assertThat(metadataMap.get(EnrichPolicyRunner.ENRICH_MATCH_FIELD_NAME), equalTo(policy.getMatchField()));
        assertThat(metadataMap.get(EnrichPolicyRunner.ENRICH_POLICY_TYPE_FIELD_NAME), equalTo(policy.getType()));