```
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
List.of(
                    new Alias(EMPTY, "b", new UnresolvedFunction(EMPTY, "min", DEFAULT, List.of(attribute("a")))),
                    attribute("c"),
                    attribute("d.e")
                )
            ),
            processingCommand("stats b = min(a) by c, d.e")
        );
    }
    public void testStatsWithoutGroups() {
        assertEquals(
            new Aggregate(
                EMPTY,
                PROCESSING_CMD_INPUT,
                List.of(),
                List.of(
                    new Alias(EMPTY, "min(a)", new UnresolvedFunction(EMPTY, "min", DEFAULT, List.of(attribute("a")))),
                    new Alias(EMPTY, "c", integer(1))
                )
            ),
            processingCommand("stats min(a), c = 1")
        );
    }
    public void testStatsWithoutAggs() throws Exception {
        assertEquals(
            new Aggregate(EMPTY, PROCESSING_CMD_INPUT, List.of(attribute("a")), List.of(attribute("a"))),
            processingCommand("stats by a")
        );
    }
    public void testStatsWithoutAggsOrGroup() throws Exception {