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 │
└────┴───────┘
```
{
        return UInt64(data[n]);
    }
    
    Int64 NO_SANITIZE_UNDEFINED getInt(size_t n) const override
    {
        return Int64(data[n]);
    }
    bool getBool(size_t n) const override
    {
        return bool(data[n]);
    }
    void insert(const Field & x) override
    {
        data.push_back(DB::get<NearestFieldType<T>>(x));
    }
    void insertRangeFrom(const IColumn & src, size_t start, size_t length) override;
    ColumnPtr filter(const IColumn::Filter & filt, ssize_t result_size_hint) const override;
    ColumnPtr permute(const IColumn::Permutation & perm, size_t limit) const override;
    ColumnPtr index(const IColumn & indexes, size_t limit) const override;
    template <typename Type>
    ColumnPtr indexImpl(const PaddedPODArray<Type> & indexes, size_t limit) const;
    ColumnPtr replicate(const IColumn::Offsets & offsets) const override;
    void getExtremes(Field & min, Field & max) const override;
    MutableColumns scatter(IColumn::ColumnIndex num_columns, const IColumn::Selector & selector) const override
    {
        return this->template scatterImpl<Self>(num_columns, selector);
    }
    void gather(ColumnGathererStream & gatherer_stream) override;
    bool canBeInsideNullable() const override { return true; }