Updating a Nullable column value by using alter .... where ... causes to set another value!

ClickHouse version: 20.6.3.28
Engine: MergeTree
OS: Ubuntu 18.04.3 LTS

Steps to reproduce:
```sql
CREATE TABLE table1(
	id int,
	price Nullable(Int32)
)
ENGINE = MergeTree()
PARTITION BY id
ORDER BY (id);
INSERT INTO table1 (id, price) VALUES (1, 100);
ALTER TABLE table1  update price = 150 where id=1;
SELECT * FROM table1;
```
We expect the price to be `150`, but it's `93148480`:

```
┌─id─┬────price─┐
│  1 │ 93148480 │
└────┴──────────┘
```
Using `Decimal(9,2)` field instead of `Int32` would set the value  `932342.88` always. It seems there's a fixed value for each data type.

If we don't use such a `where` clause, it works correctly:
```sql
ALTER TABLE db1.table1  update price = 150 where 1=1;
┌─id─┬─price─┐
│  1 │   150 │
└────┴───────┘
```
}
        ColumnPtr result_nested_column;
        {
            Block temporary_block(
            {
                arg_cond,
                {
                    getNestedColumn(arg_then.column),
                    removeNullable(arg_then.type),
                    ""
                },
                {
                    getNestedColumn(arg_else.column),
                    removeNullable(arg_else.type),
                    ""
                },
                {
                    nullptr,
                    removeNullable(block.getByPosition(result).type),
                    ""
                }
            });
            executeImpl(temporary_block, {0, 1, 2}, 3, temporary_block.rows());
            result_nested_column = temporary_block.getByPosition(3).column;
        }
        block.getByPosition(result).column = ColumnNullable::create(
            materializeColumnIfConst(result_nested_column), materializeColumnIfConst(result_null_mask));
        return true;
    }
    bool executeForNullThenElse(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count) const