```
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/main/java/org/elasticsearch/xpack/esql/parser/LogicalPlanBuilder.java
List<NamedExpression> groupings = visitGrouping(ctx.grouping());
        aggregates.addAll(groupings);
        return input -> new InlineStats(source(ctx), input, new ArrayList<>(groupings), aggregates);
    }
    @Override
    public PlanFactory visitWhereCommand(EsqlBaseParser.WhereCommandContext ctx) {
        Expression expression = expression(ctx.booleanExpression());
        return input -> new Filter(source(ctx), input, expression);
    }
    @Override
    public List<Alias> visitFields(EsqlBaseParser.FieldsContext ctx) {
        return ctx != null ? visitList(this, ctx.field(), Alias.class) : new ArrayList<>();
    }
    @Override
    public PlanFactory visitLimitCommand(EsqlBaseParser.LimitCommandContext ctx) {
        Source source = source(ctx);
        int limit = Integer.parseInt(ctx.INTEGER_LITERAL().getText());
        return input -> new Limit(source, new Literal(source, limit, DataTypes.INTEGER), input);
    }
    @Override
    public PlanFactory visitSortCommand(EsqlBaseParser.SortCommandContext ctx) {
        List<Order> orders = visitList(this, ctx.orderExpression(), Order.class);
        Source source = source(ctx);
        return input -> new OrderBy(source, input, orders);
    }
    @Override
    public Explain visitExplainCommand(EsqlBaseParser.ExplainCommandContext ctx) {
        return new Explain(source(ctx), plan(ctx.subqueryExpression().query()));
    }
    @Override