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 (nodes_mapping.count(predicate))
            continue;
        stack.push({.node = predicate});
        while (!stack.empty())
        {
            auto & cur = stack.top();
            
            while (cur.next_child_to_visit < cur.node->children.size())
            {
                const auto * child = cur.node->children[cur.next_child_to_visit];
                if (nodes_mapping.count(child) == 0)
                {
                    stack.push({.node = child});
                    break;
                }
                ++cur.next_child_to_visit;
            }
            if (cur.next_child_to_visit == cur.node->children.size())
            {
                auto & node = actions->nodes.emplace_back(*cur.node);
                nodes_mapping[cur.node] = &node;
                for (auto & child : node.children)
                    child = nodes_mapping[child];
                if (node.type == ActionType::INPUT)
                    required_inputs[node.result_name].push_back(&node);
                stack.pop();
            }
        }
    }
    const Node * result_predicate = nodes_mapping[*conjunction.begin()];