```
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
EMPTY,
                PROCESSING_CMD_INPUT,
                List.of(new Alias(EMPTY, "b", attribute("a")), new Alias(EMPTY, "c", new Add(EMPTY, attribute("a"), integer(1))))
            ),
            processingCommand("eval b = a, c = a + 1")
        );
    }
    public void testEvalImplicitNames() {
        assertEquals(new Eval(EMPTY, PROCESSING_CMD_INPUT, List.of(new Alias(EMPTY, "a", attribute("a")))), processingCommand("eval a"));
        assertEquals(
            new Eval(
                EMPTY,
                PROCESSING_CMD_INPUT,
                List.of(
                    new Alias(
                        EMPTY,
                        "fn(a+1)",
                        new UnresolvedFunction(EMPTY, "fn", DEFAULT, List.of(new Add(EMPTY, attribute("a"), integer(1))))
                    )
                )
            ),
            processingCommand("eval fn(a + 1)")
        );
    }
    public void testStatsWithGroups() {
        assertEquals(
            new Aggregate(
                EMPTY,
                PROCESSING_CMD_INPUT,
                List.of(attribute("c"), attribute("d.e")),