### Elasticsearch Version

8.11.0

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

MacOS

### Problem Description

When sending a ESQL query with the `enrich` command that involves a policy that does not existing a `NullPointerException` is thrown and shown as error messages to the user:

Query:
```
row a  = 1| enrich missing-policy
```

Returns:
```
null_pointer_exception - Cannot invoke "org.elasticsearch.xpack.core.enrich.EnrichPolicy.getMatchField()" because "policy" is null
```

### Steps to Reproduce

See above.

### Logs (if relevant)

_No response_
x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/analysis/AnalyzerTests.java
"unsigned_long",
            "unsupported",
            "x",
            "x.y",
            "x.y.z",
            "x.y.z.v",
            "x.y.z.w"
        );
    }
    public void testDropWildcardDottedField2() {
        assertProjectionWithMapping(
            """
                from test
                | drop some.*
                """,
            "mapping-multi-field-with-nested.json",
            "binary",
            "binary_stored",
            "bool",
            "date",
            "date_nanos",
            "geo_shape",
            "int",
            "keyword",
            "shape",
            "text",
            "unsigned_long",
            "unsupported",
            "x",
            "x.y",