A cast in Laravel should only affect the type, but not the database intrinsics whether a column accepts `null` or not.
As an example, consider this table (Postgres syntax):
```sql
CREATE TABLE foo (
some_column jsonb
);
```
This will be generated as: `@property string|null $some_column`
When providing a the following casts on the model:
```php
protected $casts = [
'some_column' => 'array',
];
```
then the generated property changes to: `@property array $some_column`
However the DB still accepts `null`, but this can't be expressed via the casts.
This change will make the null "sticky" and generate: `@property array|null $some_column`
