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)).
```

}
    
    auto it = inputs.begin();
    for (; it != inputs.end(); ++it)
        if (*it == col)
            break;
    if (it == inputs.end())
        return false;
    
    for (const auto & node : nodes)
        for (const auto * child : node.children)
            if (col == child)
                return false;
    
    for (const auto * node : index)
        if (col == node)
            return false;
    
    for (auto jt = nodes.begin(); jt != nodes.end(); ++jt)
    {
        if (&(*jt) == *it)
        {
            nodes.erase(jt);
            break;
        }
    }
    inputs.erase(it);
    return true;
}
ActionsDAGPtr ActionsDAG::clone() const