### 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
}
    public void testUnsupportedFieldAfterProject() {
        var errorMessage = "Cannot use field [unsupported] with unsupported type [ip_range]";
        verifyUnsupported("""
            from test
            | keep unsupported
            | eval x = unsupported
            """, errorMessage);
    }
    public void testUnsupportedFieldEvalAfterProject() {
        var errorMessage = "Cannot use field [unsupported] with unsupported type [ip_range]";
        verifyUnsupported("""
            from test
            | keep unsupported
            | eval x = unsupported + 1
            """, errorMessage);
    }
    public void testUnsupportedFieldFilterAfterProject() {
        var errorMessage = "Cannot use field [unsupported] with unsupported type [ip_range]";
        verifyUnsupported("""
            from test
            | keep unsupported
            | where unsupported == null
            """, errorMessage);
    }
    public void testUnsupportedFieldFunctionAfterProject() {
        var errorMessage = "Cannot use field [unsupported] with unsupported type [ip_range]";
        verifyUnsupported("""
            from test
            | keep unsupported