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 * node : index)
        if (node->result_name == column_name)
            return true;
    for (auto it = nodes.rbegin(); it != nodes.rend(); ++it)
    {
        auto & node = *it;
        if (node.result_name == column_name)
        {
            index.push_back(&node);
            return true;
        }
    }
    return false;
}
bool ActionsDAG::removeUnusedResult(const std::string & column_name)
{
    
    const Node * col;
    {
        auto it = index.begin();
        for (; it != index.end(); ++it)
            if ((*it)->result_name == column_name)
                break;
        if (it == index.end())
            throw Exception(ErrorCodes::LOGICAL_ERROR, "Not found result {} in ActionsDAG\n{}", column_name, dumpDAG());
        col = *it;
        index.erase(it);