### 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
""", "Found 1 problem\n" + "line 2:8: No match found for [dep.*]", "mapping-multi-field-with-nested.json");
    }
    public void testSupportedDeepHierarchy() {
        assertProjectionWithMapping("""
            from test
            | keep some.dotted.field, some.string.normalized
            """, "mapping-multi-field-with-nested.json", "some.dotted.field", "some.string.normalized");
    }
    public void testDropSupportedDottedField() {
        assertProjectionWithMapping(
            """
                from test
                | drop some.dotted.field
                """,
            "mapping-multi-field-variation.json",
            "bool",
            "date",
            "date_nanos",
            "float",
            "foo_type",
            "int",
            "keyword",
            "point",
            "shape",
            "some.ambiguous",
            "some.ambiguous.normalized",
            "some.ambiguous.one",
            "some.ambiguous.two",
            "some.string",
            "some.string.normalized",