Answered modObjectUpdateProcessor throws "_err_ns" error when attempting to retrieve the primaryKeyField

$primaryKey = $this->getProperty($this->primaryKeyField,false);
if (empty($primaryKey)) return $this->modx->lexicon($this->objectType.'_err_ns');

class GalleryUpdateProcessor extends modObjectUpdateProcessor {
    public $classKey = 'galleries';
    public $languageTopics = array('project:default');
    public $objectType = 'project';
}
return 'GalleryUpdateProcessor';

    <object class="galleries" table="project_galleries" extends="xPDOSimpleObject">
        <field key="galleryname" dbtype="varchar" precision="250" phptype="string" null="true" default="" />
        <field key="description" dbtype="text" phptype="string" />
        <field key="artworktotal" dbtype="int" precision="10" phptype="integer" null="true" default="0" />
        <field key="url" dbtype="varchar" precision="255" phptype="string" null="true" default="" />
        <field key="enabled" dbtype="int" precision="1" phptype="integer" null="true" default="0" />
        <field key="phase" dbtype="int" precision="1" phptype="integer" attributes="unsigned" null="false" default="0" />
        <field key="type" dbtype="int" precision="1" phptype="integer" attributes="unsigned" null="false" default="0" />
        <field key="cover_filename" dbtype="varchar" precision="250" phptype="string" null="true" default="" />
        <field key="vote_on" dbtype="int" precision="1" phptype="integer" attributes="unsigned" null="true" default="" />
        <field key="votes" dbtype="int" precision="10" phptype="integer" null="true" default="0" />
        <field key="createdon" dbtype="datetime" phptype="datetime" null="true" />
        <field key="createdby" dbtype="int" precision="10" phptype="integer" attributes="unsigned" null="true" default="0" />
        <composite alias="Artwork" class="artworks" local="id" foreign="gallery_id" cardinality="many" owner="local" />
        <aggregate alias="CreatedBy" class="modUser" local="createdby" foreign="id" cardinality="one" owner="foreign" />
    </object>