You have to provide the following information whenever possible.

**Describe the bug**
This query fails with the latest stable version 21.5.5.12. It worked with the last stable version 21.4.7.3.

**Does it reproduce on recent release?**
yes

**How to reproduce**
21.5.5.12

```
SELECT
    label,
    number
FROM
(
    SELECT
        'a' AS label,
        number
    FROM
    (
        SELECT number
        FROM numbers(10)
    )
    UNION ALL
    SELECT
        'b' AS label,
        number
    FROM
    (
        SELECT number
        FROM numbers(10)
    )
)
WHERE number IN
(
    SELECT number
    FROM numbers(5)
)
```

**Expected behavior**
Query should run without errors

**Error message and/or stacktrace**
```
Received exception from server (version 21.5.5):
Code: 49. DB::Exception: Received from localhost:9000. DB::Exception: Block structure mismatch in Pipe::unitePipes stream: different names of columns:
label String String(size = 0), number UInt64 UInt64(size = 0), 'b' String Const(size = 0, String(size = 1))
label String String(size = 0), number UInt64 UInt64(size = 0), 'a' String Const(size = 0, String(size = 1)).
```

{
    for (const auto & input : inputs_)
    {
        if (input.column && isColumnConst(*input.column))
        {
            addInput(input);
            
            
            
            
            
            
            index.push_back(&addColumn(input));
        }
        else
            index.push_back(&addInput(input.name, input.type));
    }
}
ActionsDAG::Node & ActionsDAG::addNode(Node node)
{
    auto & res = nodes.emplace_back(std::move(node));
    if (res.type == ActionType::INPUT)
        inputs.emplace_back(&res);
    return res;
}
const ActionsDAG::Node & ActionsDAG::addInput(std::string name, DataTypePtr type)