### 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 testDateExtractWithSwappedArguments() {
        verifyUnsupported("""
            from test
            | eval date_extract(date, "year")
            """, "function definition has been updated, please swap arguments in [date_extract(date, \"year\")]");
    }
    public void testDateFormatWithSwappedArguments() {
        verifyUnsupported("""
            from test
            | eval date_format(date, "yyyy-MM-dd")
            """, "function definition has been updated, please swap arguments in [date_format(date, \"yyyy-MM-dd\")]");
    }
    public void testDateTruncWithSwappedArguments() {
        verifyUnsupported("""
            from test
            | eval date_trunc(date, 1 month)
            """, "function definition has been updated, please swap arguments in [date_trunc(date, 1 month)]");
    }
    public void testDateTruncWithDateInterval() {
        verifyUnsupported("""
            from test
            | eval date_trunc(date, date)
            """, "second argument of [date_trunc(date, date)] must be [dateperiod or timeduration], found value [date] type [datetime]");
    }
    
    public void testAggsWithDuplicatesAndNonExistingFunction() throws Exception {
        verifyUnsupported("""
            row a = 1, b = 2
            | stats x = non_existing(a), x = count(a) by b
            """, "Unknown function [non_existing]");