CakePHP“试图获得非对象的属性”;错误

当我发布表单时，它显示错误:

Trying to get property of non-object [APP'Controller'UsersController.php, line 647].

下面是ctp文件格式代码:

admin_highlightedstylist。ctp是

    <?php echo $this->Form->create('Userhighlighted'); ?>
                    <tr>
                        <th>STYLIST LIST</th>
                        <th><?php echo $this->Form->input('stylist_id', array('empty' => 'Select Stylist')); ?></th>
                        <th>
                            <div class="submit">
                                <?php echo $this->Form->end('ADD HIGHLIGHTED'); ?>
                            </div>
                        </th>
                    </tr>

这里是控制器代码脚本，UserController.php

    public function admin_highlightedstylist(){
            $this->layout = 'admin';
            $this->isAdmin();
            if($this->request->is('post')){
                print_r($this->requert->data['Userhighlighted']['stylist_id']);
                exit;
            }
            $stylists = $this->User->find('list', array('conditions'=>array('is_stylist' => true,)));
            $this->set(compact('id', 'stylists'));

        }

如何删除此错误以及如何解决此错误?