### 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
var filter = as(limit.child(), Filter.class);
            var eval = as(filter.child(), Eval.class);
            limit = as(eval.child(), Limit.class);
            as(limit.child(), EsRelation.class);
        }
    }
    public void testImplicitDefaultLimitAfterLimitAndBreaker() {
        for (var breaker : List.of("stats c = count(salary) by last_name", "sort salary")) {
            var plan = analyze("from test | limit 100000 | " + breaker);
            var limit = as(plan, Limit.class);
            assertThat(limit.limit().fold(), equalTo(MAX_LIMIT));
        }
    }
    public void testImplicitDefaultLimitAfterBreakerAndNonBreakers() {
        for (var breaker : List.of("stats c = count(salary) by last_name", "eval c = salary | sort c")) {
            var plan = analyze("from test | " + breaker + " | eval cc = c * 10 | where cc > 0");
            var limit = as(plan, Limit.class);
            assertThat(limit.limit().fold(), equalTo(DEFAULT_LIMIT));
        }
    }
    private static final String[] COMPARISONS = new String[] { "==", "!=", "<", "<=", ">", ">=" };
    public void testCompareIntToString() {
        for (String comparison : COMPARISONS) {
            var e = expectThrows(VerificationException.class, () -> analyze("""
                from test
                | where emp_no COMPARISON "foo"
                """.replace("COMPARISON", comparison)));
            assertThat(
                e.getMessage(),
                containsString(