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)).
```

if (it != inputs_map.end())
                node = it->second;
        }
    }
    
    if (second.project_input)
    {
        first.index.swap(second.index);
        first.project_input = true;
    }
    else
    {
        
        for (const auto * node : first.index)
        {
            auto it = removed_first_result.find(node);
            if (it != removed_first_result.end() && it->second > 0)
                --it->second;
            else
                second.index.push_back(node);
        }
        first.index.swap(second.index);
    }
    first.nodes.splice(first.nodes.end(), std::move(second.nodes));
    first.projected_output = second.projected_output;
    
    first.removeUnusedActions();
    return std::make_shared<ActionsDAG>(std::move(first));
}
ActionsDAG::SplitResult ActionsDAG::split(std::unordered_set<const Node *> split_nodes) const