**Describe what's wrong**

Query with rollup using same selected field name as the name of underlying column reports structure mismatch

**Does it reproduce on recent release?**

yes

**How to reproduce**

`21.9.2.17`

```sql
CREATE TABLE test
(
    `d` DateTime,
    `a` LowCardinality(String),
    `b` UInt64
)
ENGINE = MergeTree
PARTITION BY toDate(d)
ORDER BY d;

SELECT *
FROM (
    SELECT
        a,
        max((d, b)).2 AS value
    FROM test
    GROUP BY rollup(a)
)
WHERE a <> '';
```

**Expected behavior**

This used to return an ok result on v21.8

**Error message and/or stacktrace**

> Code: 352. DB::Exception: Block structure mismatch in (columns with identical name must have identical structure) stream: different columns:
> notEquals(a, '') LowCardinality(UInt8) ColumnLowCardinality(size = 0, UInt8(size = 0), ColumnUnique(size = 1, UInt8(size = 1)))
> notEquals(a, '') LowCardinality(UInt8) Const(size = 0, ColumnLowCardinality(size = 1, UInt8(size = 1), ColumnUnique(size = 2, UInt8(size = 2)))). (AMBIGUOUS_COLUMN_NAME) (version 21.9.2.17 (official build))



}
    if (before_order_by)
    {
        ss << "before_order_by " << before_order_by->dumpDAG() << "\n";
    }
    if (before_limit_by)
    {
        ss << "before_limit_by " << before_limit_by->dumpDAG() << "\n";
    }
    if (final_projection)
    {
        ss << "final_projection " << final_projection->dumpDAG() << "\n";
    }
    if (!selected_columns.empty())
    {
        ss << "selected_columns ";
        for (size_t i = 0; i < selected_columns.size(); i++)
        {
            if (i > 0)
            {
                ss << ", ";
            }
            ss << backQuote(selected_columns[i]);
        }
        ss << "\n";
    }
    return ss.str();
}
}