**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))



const Block & header,
    bool overflow_row_,
    const ExpressionActionsPtr & expression_,
    const std::string & filter_column_,
    TotalsMode totals_mode_,
    double auto_include_threshold_,
    bool final_)
    : ISimpleTransform(header, transformHeader(header, expression_  ? &expression_->getActionsDAG() : nullptr, final_), true)
    , overflow_row(overflow_row_)
    , expression(expression_)
    , filter_column_name(filter_column_)
    , totals_mode(totals_mode_)
    , auto_include_threshold(auto_include_threshold_)
    , final(final_)
{
    if (!filter_column_name.empty())
        filter_column_pos = outputs.front().getHeader().getPositionByName(filter_column_name);
    finalized_header = getInputPort().getHeader();
    finalizeBlock(finalized_header);
    
    if (expression)
    {
        auto totals_header = finalized_header;
        size_t num_rows = totals_header.rows();
        expression->execute(totals_header, num_rows);
        outputs.emplace_back(totals_header, this);
    }
    else
        outputs.emplace_back(finalized_header, this);