### 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 testCompareStringToDate() {
        for (String comparison : COMPARISONS) {
            assertProjectionWithMapping("""
                from test
                | where "1985-01-01T00:00:00Z" COMPARISON date
                | keep date
                """.replace("COMPARISON", comparison), "mapping-multi-field-variation.json", "date");
        }
    }
    public void testCompareDateToStringFails() {
        for (String comparison : COMPARISONS) {
            verifyUnsupported("""
                from test
                | where date COMPARISON "not-a-date"
                | keep date
                """.replace("COMPARISON", comparison), "Invalid date [not-a-date]", "mapping-multi-field-variation.json");
        }
    }
    public void testDateFormatOnInt() {
        verifyUnsupported("""
            from test
            | eval date_format(int)
            """, "first argument of [date_format(int)] must be [datetime], found value [int] type [integer]");
    }
    public void testDateFormatOnFloat() {
        verifyUnsupported("""
            from test
            | eval date_format(float)
            """, "first argument of [date_format(float)] must be [datetime], found value [float] type [double]");
    }