```
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
private LogicalPlan processingCommand(String e) {
        return parser.createStatement("row a = 1 | " + e);
    }
    private static final LogicalPlan PROCESSING_CMD_INPUT = new Row(EMPTY, List.of(new Alias(EMPTY, "a", integer(1))));
    private static UnresolvedAttribute attribute(String name) {
        return new UnresolvedAttribute(EMPTY, name);
    }
    private static ReferenceAttribute referenceAttribute(String name, DataType type) {
        return new ReferenceAttribute(EMPTY, name, type);
    }
    private static Literal integer(int i) {
        return new Literal(EMPTY, i, DataTypes.INTEGER);
    }
    private static Literal integers(int... ints) {
        return new Literal(EMPTY, Arrays.stream(ints).boxed().toList(), DataTypes.INTEGER);
    }
    private static Literal literalLong(long i) {
        return new Literal(EMPTY, i, DataTypes.LONG);
    }
    private static Literal literalLongs(long... longs) {
        return new Literal(EMPTY, Arrays.stream(longs).boxed().toList(), DataTypes.LONG);
    }
    private static Literal literalDouble(double d) {
        return new Literal(EMPTY, d, DataTypes.DOUBLE);
    }
    private static Literal literalDoubles(double... doubles) {
        return new Literal(EMPTY, Arrays.stream(doubles).boxed().toList(), DataTypes.DOUBLE);
    }
    private static Literal literalUnsignedLong(String ulong) {
        return new Literal(EMPTY, asLongUnsigned(new BigInteger(ulong)), DataTypes.UNSIGNED_LONG);