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 (size_t i = 0; i < aliases.size(); ++i)
    {
        const auto & item = aliases[i];
        const auto * child = required_nodes[i];
        if (!item.second.empty() && item.first != item.second)
        {
            Node node;
            node.type = ActionType::ALIAS;
            node.result_type = child->result_type;
            node.result_name = std::move(item.second);
            node.column = child->column;
            node.children.emplace_back(child);
            child = &addNode(std::move(node));
        }
        auto it = names_map.find(child->result_name);
        if (it == names_map.end())
        {
            names_map[child->result_name] = index.size();
            index.push_back(child);
        }
        else
            index[it->second] = child;
    }
}
void ActionsDAG::project(const NamesWithAliases & projection)
{
    std::unordered_map<std::string_view, const Node *> names_map;
    for (const auto * node : index)
        names_map.emplace(node->result_name, node);