Reproduction steps:
```
CREATE TABLE table_left                                                                                                                                                                                              
(                                                                                                                                                                                                                    
    `date` Date,                                                                                                                                                                                                     
    `uid` String                                                                                                                                                                                                     
)                                                                                                                                                                                                                    
ENGINE = MergeTree()                                                                                                                                                                                                 
ORDER BY (date, uid)          
                                                                                                                                                                                       
CREATE TABLE table_right                                                                                                                                                                                             
(                                                                                                                                                                                                                    
    `date` Date,                                                                                                                                                                                                     
    `value` Decimal(18, 10)                                                                                                                                                                                          
)                                                                                                                                                                                                                    
ENGINE = MergeTree()                                                                                                                                                                                                 
ORDER BY date

INSERT INTO table_left values(toDate('2019-10-01'), 'hello');
INSERT INTO table_right values (toDate('2019-10-01'), 1), (toDate('2029-10-01'), 2);

SET join_use_nulls = 1;

SELECT ifNull(subquery_right.alias_value, 0)
FROM table_left
FULL OUTER JOIN 
(
    SELECT
        date,
        value AS alias_value
    FROM table_right
) AS subquery_right
ON table_left.date = subquery_right.date

Received exception from server (version 21.3.1):
Code: 43. DB::Exception: Received from localhost:9000. DB::Exception: Incompatible types of arguments corresponding to two conditional branches: while executing 'FUNCTION ifNull(alias_value :: 0, 0 :: 1) -> ifNull(alias_value, 0) Decimal(18, 10) : 2'. 
```
{
        size_t size = cond.size();
        auto col_res = ColVecResult::create(size);
        typename ColVecResult::Container & res = col_res->getData();
        for (size_t i = 0; i < size; ++i)
            res[i] = cond[i] ? static_cast<ResultType>(a[i]) : static_cast<ResultType>(b[i]);
        return col_res;
    }
    static ColumnPtr vectorConstant(const ArrayCond & cond, const ArrayA & a, B b, UInt32)
    {
        size_t size = cond.size();
        auto col_res = ColVecResult::create(size);
        typename ColVecResult::Container & res = col_res->getData();
        for (size_t i = 0; i < size; ++i)
            res[i] = cond[i] ? static_cast<ResultType>(a[i]) : static_cast<ResultType>(b);
        return col_res;
    }
    static ColumnPtr constantVector(const ArrayCond & cond, A a, const ArrayB & b, UInt32)