Multipick List error getting value

Problem/Motivation

A PHP Fatal error occurs when trying to push data to Salesforce if dealing with a multipickfield.

php.ERROR: TypeError: Argument 2 passed to Drupal\typed_data\DataFetcher::fetchDataBySubPaths() must be of the type array, null given, called in /app/web/modules/contrib/typed_data/src/DataFetcher.php on line 32 in Drupal\typed_data\DataFetcher->fetchDataBySubPaths()

In our case, Salesforce is passing an object to a Typed Data module function which is expecting a string, and Typed Data is attempting to explode that object, which gives us Null which kicks up this error.

(Honestly, I'm not sure if this is a Typed Data issue, or a Salesforce issue.)

Steps to reproduce

If you have a mapping for Drupal ListStringItem fieldtypes to multipickfields in Salesforce. This happens on Push.

This appeared after the core update of 8.9.14... but I can't verify it was actually caused by that.

Proposed resolution

Changing one line in src/Plugin/SalesforceMappingField/PropertiesBase::value seemed to fix this for me. (see CHANGE HERE below)

/**
   * {@inheritdoc}
   */
  public function value(EntityInterface $entity, SalesforceMappingInterface $mapping) {
    // No error checking here. If a property is not defined, it's a
    // configuration bug that needs to be solved elsewhere.
    // Multipicklist is the only target type that handles multi-valued fields.
    $describe = $this
      ->salesforceClient
      ->objectDescribe($mapping->getSalesforceObjectType());
    $field_definition = $describe->getField($this->config('salesforce_field'));
    if ($field_definition['type'] == 'multipicklist') {
      $values = [];
      foreach ($entity->get($this->config('drupal_field_value')) as $value) {
        // CHANGE HERE
        //$values[] = $this->getStringValue($entity, $value);
        $values[] = $this->getStringValue($entity, $value->value);

      }
      return implode(';', $values);
    }
    else {
      return $this->getStringValue($entity, $this->config('drupal_field_value'));
    }
  }

But I feel like I'm missing something, because I can't imagine the method to get the value of a ListStringItem would have changed?

Remaining tasks

User interface changes

API changes

Data model changes