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 │
└────┴───────┘
```
{
        data.reserve(n);
    }
    const char * getFamilyName() const override { return TypeName<T>::get(); }
    TypeIndex getDataType() const override { return TypeId<T>::value; }
    MutableColumnPtr cloneResized(size_t size) const override;
    Field operator[](size_t n) const override
    {
        assert(n < data.size()); 
        return data[n];
    }
    void get(size_t n, Field & res) const override
    {
        res = (*this)[n];
    }
    UInt64 get64(size_t n) const override;
    Float64 getFloat64(size_t n) const override;
    Float32 getFloat32(size_t n) const override;
    
    UInt64 NO_SANITIZE_UNDEFINED getUInt(size_t n) const override