PHP 8.4 Implicitly marking parameter as nullable is deprecated

Problem/Motivation

PHP Deprecated: Drupal\field_validation\Form\FieldValidationRuleAddForm::buildForm(): Implicitly marking parameter $field_validation_rule_set as nullable is deprecated, the explicit nullable type must be used instead in /var/www/html/web/modules/contrib/field_validation/src/Form/FieldValidationRuleAddForm.php on line 53

PHP Deprecated: Drupal\field_validation\Form\FieldValidationRuleFormBase::buildForm(): Implicitly marking parameter $field_validation_rule_set as nullable is deprecated, the explicit nullable type must be used instead in /var/www/html/web/modules/contrib/field_validation/src/Form/FieldValidationRuleFormBase.php on line 111

PHP Deprecated: Drupal\field_validation\Form\FieldValidationRuleEditForm::buildForm(): Implicitly marking parameter $field_validation_rule_set as nullable is deprecated, the explicit nullable type must be used instead in /var/www/html/web/modules/contrib/field_validation/src/Form/FieldValidationRuleEditForm.php on line 16

PHP Deprecated: Drupal\field_validation\Form\FieldValidationRuleDeleteForm::buildForm(): Implicitly marking parameter $field_validation_rule_set as nullable is deprecated, the explicit nullable type must be used instead in /var/www/html/web/modules/contrib/field_validation/src/Form/FieldValidationRuleDeleteForm.php on line 59

Steps to reproduce

• Enable Field Validation module.
• Run Drupal with PHP 8.4.
• Observe PHP warnings caused by implicit nullable

Proposed resolution

Update Implicitly nullable parameter types to Explicitly nullable