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)).
```

throw Exception(ErrorCodes::LOGICAL_ERROR,
                                    "Cannot find column {} in ActionsDAG result", node->result_name);
                first.inputs.push_back(node);
            }
            else
            {
                inputs_map[node] = it->second.front();
                removed_first_result[it->second.front()] += 1;
                it->second.pop_front();
            }
        }
    }
    
    for (auto & node : second.nodes)
    {
        for (auto & child : node.children)
        {
            if (child->type == ActionType::INPUT)
            {
                auto it = inputs_map.find(child);
                if (it != inputs_map.end())
                    child = it->second;
            }
        }
    }
    for (auto & node : second.index)
    {
        if (node->type == ActionType::INPUT)
        {
            auto it = inputs_map.find(node);