Jane version(s) affected: ^7.5

Description
When using nullable date or date time definitions the generated normalize method will throw a fatal error because a mandatory null check is missing:

Call to a member function format() on null

How to reproduce

schema:

dateProperty:
type: string
nullable: true
format: date
example: 2020-01-01

generated code in normalizer

$data['dateProperty'] = $object->getDateProperty()->format('Y-m-d');

Possible Solution

possible solution for php7.2 and php8:

$data['dateProperty'] = $object->getDateProperty() ? $object->getDateProperty()->format('Y-m-d') : null;

Additional context

Fix should be implemented in createNormalizationValueStatement in Guesser\Guess\Date(Time)?Type