### 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/main/java/org/elasticsearch/xpack/esql/analysis/Analyzer.java
if (matches.isEmpty()) {
            UnresolvedAttribute unresolved;
            var name = u.name();
            if (Regex.isSimpleMatchPattern(name)) {
                unresolved = u.withUnresolvedMessage(format(null, "No match found for [{}]", name));
            } else {
                Set<String> names = new HashSet<>(attrList.size());
                for (var a : attrList) {
                    String nameCandidate = a.name();
                    if (EsqlDataTypes.isPrimitive(a.dataType())) {
                        names.add(nameCandidate);
                    }
                }
                unresolved = u.withUnresolvedMessage(UnresolvedAttribute.errorMessage(name, StringUtils.findSimilar(name, names)));
            }
            return singletonList(unresolved);
        }
        return matches;
    }
    private static Attribute handleSpecialFields(UnresolvedAttribute u, Attribute named) {
        if (named instanceof FieldAttribute fa) {
            
            var field = fa.field();
            if (field instanceof InvalidMappedField imf) {
                named = u.withUnresolvedMessage("Cannot use field [" + fa.name() + "] due to ambiguities being " + imf.errorMessage());
            }
        }
        return named;
    }
    private static class ResolveFunctions extends ParameterizedAnalyzerRule<LogicalPlan, AnalyzerContext> {