```
ROW a="b c d"
| DISSECT a "%{b} %{} %{d}"
```
returns

```
       a       |       b       |               |       d       
---------------+---------------+---------------+---------------
b c d          |b              |null           |d 
```

it should ignore the empty pattern instead, and only return `a, b, d`
x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/parser/StatementParserTests.java
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0; you may not use this file except in compliance with the Elastic License
 * 2.0.
 */
package org.elasticsearch.xpack.esql.parser;
import org.elasticsearch.core.Tuple;
import org.elasticsearch.test.ESTestCase;
import org.elasticsearch.xpack.esql.evaluator.predicate.operator.comparison.Equals;
import org.elasticsearch.xpack.esql.evaluator.predicate.operator.comparison.GreaterThan;
import org.elasticsearch.xpack.esql.evaluator.predicate.operator.comparison.GreaterThanOrEqual;
import org.elasticsearch.xpack.esql.evaluator.predicate.operator.comparison.LessThan;
import org.elasticsearch.xpack.esql.evaluator.predicate.operator.comparison.LessThanOrEqual;
import org.elasticsearch.xpack.esql.evaluator.predicate.operator.regex.RLike;
import org.elasticsearch.xpack.esql.evaluator.predicate.operator.regex.WildcardLike;
import org.elasticsearch.xpack.esql.expression.predicate.operator.arithmetic.Add;
import org.elasticsearch.xpack.esql.plan.logical.Dissect;
import org.elasticsearch.xpack.esql.plan.logical.Enrich;
import org.elasticsearch.xpack.esql.plan.logical.EsqlUnresolvedRelation;
import org.elasticsearch.xpack.esql.plan.logical.Eval;
import org.elasticsearch.xpack.esql.plan.logical.Explain;
import org.elasticsearch.xpack.esql.plan.logical.Grok;
import org.elasticsearch.xpack.esql.plan.logical.InlineStats;
import org.elasticsearch.xpack.esql.plan.logical.MvExpand;
import org.elasticsearch.xpack.esql.plan.logical.Row;
import org.elasticsearch.xpack.ql.expression.Alias;
import org.elasticsearch.xpack.ql.expression.EmptyAttribute;
import org.elasticsearch.xpack.ql.expression.Literal;