Error normalizing root taxonomy terms

Problem/Motivation

I am using the Default Content Deploy module to export entities into code and I'm running into a normalization issue with taxonomy terms. I get the following error when exporting a root term (no parent).

Error: Call to a member function getEntityType() on null in Drupal\hal\Normalizer\EntityReferenceItemNormalizer->normalize() (line 86 of /var/www/html/dv13.openplus.ca/html/core/modules/hal/src/Normalizer/EntityReferenceItemNormalizer.php)

I believe this is happening on the parent field, where it tries to call the getEntity() method on a target_id value of "0", then calls getEntityType() on NULL. This only happens when serializing using the hal_json format; using the json format works as expected.

Steps to reproduce

Use Drupal's serializer service against a root term using the hal_json format.

Example:

$term = \Drupal\taxonomy\Entity\Term::load('50');
$output = \Drupal::service('serializer')->serialize($term, 'hal_json');
dpm($output);