fix(StateItem): PHP 8.4 compatibility for nullable types

Closes #3505782

src/Plugin/Field/FieldType/StateItem.php

@@ -175,14 +175,14 @@ class StateItem extends FieldItemBase implements StateItemInterface, OptionsProv
   /**
    * {@inheritdoc}
    */
-  public function getPossibleValues(AccountInterface $account = NULL) {
+  public function getPossibleValues(?AccountInterface $account = NULL) {
     return array_keys($this->getPossibleOptions($account));
   }
 
   /**
    * {@inheritdoc}
    */
-  public function getPossibleOptions(AccountInterface $account = NULL) {
+  public function getPossibleOptions(?AccountInterface $account = NULL) {
     $workflow = $this->getWorkflow();
     if (!$workflow) {
       // The workflow is not known yet, the field is probably being created.
@@ -198,14 +198,14 @@ class StateItem extends FieldItemBase implements StateItemInterface, OptionsProv
   /**
    * {@inheritdoc}
    */
-  public function getSettableValues(AccountInterface $account = NULL) {
+  public function getSettableValues(?AccountInterface $account = NULL) {
     return array_keys($this->getSettableOptions($account));
   }
 
   /**
    * {@inheritdoc}
    */
-  public function getSettableOptions(AccountInterface $account = NULL) {
+  public function getSettableOptions(?AccountInterface $account = NULL) {
     // $this->value is unpopulated due to https://www.drupal.org/node/2629932
     $field_name = $this->getFieldDefinition()->getName();
     if (!$this->getEntity()->hasField($field_name)) {