php - drupal entity implementation, there is a mistake somewhere -

i'm starting out drupal , poking around entity api. i've tried write implementation not meant production, test case.

but can't work. when try save new candidate error message: creating default object empty value in entity_form_submit_build_entity() (line 8213 of /wwwroot/drupal/public_html/includes/common.inc).

the entity not being added database. it's stupid error can't track down. if more experience me out grateful.

the audition.module file:

<?php ###database schemas function audition_schema(){   $schema['audition_candidate'] = array(     'description'=>'stores candidates audition',     'fields'=>array(       'id'=>array(         'description'=>'identifier candidate',         'type'=>'serial',         'not null'=>true,         'unsigned'=>true,       ),       'lastname'=>array(         'description'=>'candidate last name',         'type'=>'varchar',         'length'=>'50',         'not null'=>true,       ),       'firstname'=>array(         'description'=>'candidate first name',         'type'=>'varchar',         'length'=>'50',         'not null'=>true,       ),       'mailadress'=>array(         'description'=>'candidate mail adress',         'type'=>'varchar',         'length'=>'255',         'not null'=>true,       ),       'vocalgroup'=>array(         'description'=>'candidate vocal group type',         'type'=>'int',         'length'=>'small',         'not null'=>true,       ),     ),     'primary key' =>array('id'),     'label' => array('lastname','firstname'),   );    $schema['vocal_group'] = array(     'description'=>'stores different vocal groups',     'fields'=>array(       'id'=>array(         'description'=>'identifier vocal group',         'type'=>'serial',         'not null'=>true,         'unsigned'=>true,       ),       'group'=>array(         'description'=>'vocal group name',         'type'=>'varchar',         'length'=>'50',         'not null'=>true,       ),     ),     'primary key' =>array('id'),     'uri callback' => 'entity_class_uri',   );    return $schema; }  ###entities function audition_entity_info(){    $entity['candidate']= array(     'label'=>t('audition candidate'),     'plural label'=>t('audition candidates'),     'base table' => 'audition_candidate',     'entity class' => 'candidateentity',     'entity keys' => array(       'id'=>'id',       'label' => 'lastname'),     'admin ui' => array(       'path' => 'admin/candidate',       'controllerclass' => 'entitydefaultuicontroller',       'menu wildcard' => '%candidate',       'file' => 'candidate.admin.inc',     ),     'module' => 'audition',     'access callback' => 'candidate_access_callback',   );    $entity['vocalgroup'] = array(     'label' => t('audition candidate vocal group'),     'plural label' => t('vocal groups'),     'base table' => 'vocal_group',     'entity keys' => array(       'id'=>'id',     ),   );      /*dsm($entity);*/   return $entity; }  class candidateentity extends entity {   protected function defaulturi() {     return array('path' => 'candidate/' . $this->identifier());   } }  function candidate_access_callback($op, $candidate = null, $account= null){   if($op == 'view' && user_access('view_candidates',$account))   {     return true;   }   else if(user_access('administer_candidates',$account))   {     return true;   }    return false; }  ###install script   ###permissions function audition_permission(){   $permission['administer_candidates'] = array(     'title' => t('edit candidates'),     'description' => t('can make changes candidate date'),   );    $permission['view_candidates'] = array(     'title'=> t('view candidates'),     'description' => t('can view candidates')   );    return $permission; }  ###menu hooks function audition_menu(){     $menuitems['audition'] = array(     'page callback'=> 'audition_page',     'access callback' => true,   );    $menuitems['candidate/%candidate'] = array(     'title' => 'audition candidate',     'page callback' => 'candidate_entity_view',     'page arguments' => array(1),     'access callback' => true,   );    return $menuitems; }  ###page callback functions   function audition_page() {     $candidate= entity_load('candidate', array(1));     /*dsm($candidate);*/      return 'test';   }    function candidate_load($candidateid)   {     $candidate = entity_load('candidate',array($candidateid));     dsm($candidate);     return array_pop($candidate);   }    function candidate_entity_view($candidate)   {     return 'test';   } 

and candidate.admin.inc:

  <?php  /*   * change license header, choose license headers in project properties.  * change template file, choose tools | templates  * , open template in editor.  */  function candidate_form($form, &$form_state, $candidate){   $form['lastname'] = array(     '#title' => t('last name'),     '#type' => 'textfield',     '#default_value' => isset($candidate->lastname) ? $candidate->lastname : '',     '#description' => 'fill out last name',     '#required' => true,   );   $form['firstname'] = array(     '#title' => t('first name'),     '#type' => 'textfield',     '#default_value' => isset($candidate->firstname) ? $candidate->firstname : '',     '#description' => 'fill out first name',     '#required' => true,   );   $form['mailadress'] = array(     '#title' => t('mailadress'),     '#type' => 'textfield',     '#default_value' => isset($candidate->mailadress) ? $candidate->mailadress : '',     '#description' => 'fill out valid mailadress',     '#required' => true,   );     $form['vocalgroup'] = array(     '#title' => t('vocal group'),     '#type' => 'textfield',     '#default_value' => isset($candidate->vocalgroup) ? $candidate->vocalgroup : '',     '#description' => 'to wich vocal group belong?',     '#required' => true,   );     $form['actions'] = array(       '#type' => 'actions',       'submit' => array(         '#type' => 'submit',         '#value' => t('submit'),       ),     );    return $form;  }  function candidate_form_submit($form, &$form_state){    $candidate = entity_ui_form_submit_build_entity($form, $form_state);   dsm($candidate);   $candidate->save();    drupal_set_message(t('you created candidate'));   $form_state['redirect'] = 'admin/candidate'; }