Image le téléchargement en utilisant codeigniter du téléchargement du fichier de classe

Ce n'est pas une façon de télécharger l'image de la question . J'ai presque réussi à ajouter une image en fonction d'importation dans mon ajouter la fonction client . Il fonctionne bien lorsque je tente de télécharger un fichier valide .. mais lorsque je sélectionne un fichier non valide ou taille de fichier puis il montre undefined variable upload_data et codeigniter erreur de base de données où img_path est NULL il dit Column 'img_path' cannot be null. pourquoi cette fonction ne fonctionne pas $this->upload->display_errors(); . Les erreurs de validation montrent bien, mais pas de fichier d'erreur de validation qui se montre.

J'utilise Codeigniter et hmvc

voici mon contrôleur

<?php
class Clients extends MX_Controller{
function __construct(){
parent::__construct();
$this->load->model('mdl_clients');
}
function add(){
$data['success'] = null;
$data['errors']= null;
if($_POST){
$config_arr = array(
'upload_path'   => './uploads/',
'allowed_types' => 'gif|jpg|png',
'max_size'      => '2048',
'max_width'     => '1024',
'max_height'    => '768',
'encrypt_name'  => true,
);         
$this->load->library('upload', $config_arr);
if (!$this->upload->do_upload()) {
$data['errors'] = $this->upload->display_errors(); //this isn't working
} else {
$upload_data = $this->upload->data();
}
$config=array(
array(
'field'=>'firstName',
'label'=>'First Name',
'rules'=>'required|max_length[15]|min_length[3]'
),
array(
'field'=>'city',
'label'=>'City',
'rules'=>'required'
),
array(
'field'=>'mobile_phone',
'label'=>'Mobile Number',
'rules'=>'required'
),
array(
'field'=>'email',
'label'=>'Email',
'rules'=>'required|is_unique[clients.email]|valid_email'
),
);
$this->load->library('form_validation');
$this->form_validation->set_rules($config);
if($this->form_validation->run() == FALSE){
$data['errors'] = validation_errors();
}else{
$data=array(
'img_path'=>$upload_data['file_name'],
'firstName'=>$_POST['firstName'],
'email'=>$_POST['email'],
'city'=>$_POST['city'],
'mobile_phone'=>$_POST['mobile_phone'],
);
$this->mdl_clients->add($data);
$data['success'] = 1;
$data['errors']= 0;
}
}
$data['title'] = 'Add Client Database';
$data['main_content'] = 'clients/add';
echo Modules::run('templates/admin', $data);
}

et mon fichier de vue .. add.php

<? if($success==1) {?>
<div class="alert alert-success">
<a class="close" data-dismiss="alert" href="#">&times;</a>
Data Has been Updated ! 
</div>
<? } ?>
<?php if($errors) { ?>
<div class="alert alert-error" >
<a class="close" data-dismiss="alert" href="#">&times;</a>
<?=$errors?>
</div>
<? } ?>
<?php $attributes = array('class' => 'form-horizontal');
echo form_open_multipart('clients/add', $attributes); ?>
<fieldset>
<!-- Address form -->
<h2>Client Information</h2>
<hr />
All Fields Marked with <span style="color: red;">*</span> is necessary .
<hr />
<!-- Upload input-->
<div class="control-group">
<label class="control-label">Upload<span style="color: red;">*</span></label>
<div class="controls">
<input name="userfile" name="userfile" type="file"
class="input-xlarge">
<p class="help-block"></p>
</div>
</div>
<!-- firstName input-->
<div class="control-group">
<label class="control-label">First Name<span style="color: red;">*</span></label>
<div class="controls">
<input id="firstName" name="firstName" type="text" placeholder="First Name"
class="input-xlarge" required>
<p class="help-block"></p>
</div>
</div>
<!-- Email input-->
<div class="control-group">
<label class="control-label">E-Mail<span style="color: red;">*</span></label>
<div class="controls">
<input id="email" name="email" type="text" placeholder="A Valid Email Address"
class="input-xlarge" required>
<p class="help-block"></p>
</div>
</div>
<!-- City input-->
<div class="control-group">
<label class="control-label">City<span style="color: red;">*</span></label>
<div class="controls">
<input id="city" name="city" type="text" placeholder="City Name"
class="input-xlarge" required>
<p class="help-block"></p>
</div>
<!-- Mobile input-->
<div class="control-group">
<label class="control-label">Mobile Number<span style="color: red;">*</span></label>
<div class="controls">
<input id="mobile_phone" name="mobile_phone" type="text" placeholder="Current Mobile Phone Number"
class="input-xlarge" required>
<p class="help-block"></p>
</div>
</div>
<!-- Button -->
<div class="control-group">
<div class="controls">
<button class="btn btn-success">Add to Database</button>
</div>
</div>
</fieldset>
</form>