Ошибка с функцией bind() - Разработка расширений для Joomla 3.x

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<b>Fatal error</b>:  Call to a member function bind() on a non-object in <b>public_html/administrator/components/com_mycomp/models/default.php</b> on line <b>30</b><br />

<input type="hidden" name="table" value="item">

<?php defined( '_JEXEC' ) or die( 'Restricted access' ); 
 
class MedsignalControllersAdditem extends JControllerBase
{
  public function execute()
  {
    $app      = JFactory::getApplication();
    $return   = array("success"=>false);

    $modelName  = $app->input->get('model', 'Item');

    $modelName  = 'MedsignalModels'.ucwords($modelName);

  	 $model = new $modelName();
   	if ( $row = $model->store() )
  	 {
  		 $return['success'] = true;
  		 $return['msg'] = JText::_('COM_MEDSIGNAL_SAVE_SUCCESS');

     $return['html'] = MedsignalHelpersView::getHtml($view, $layout, $item, $row);
  	 }else{
  		 $return['msg'] = JText::_('COM_MEDSIGNAL_SAVE_FAILURE');
  	 }
    
  	echo json_encode($return);

  }

}
?>

<?php // no direct access

defined( '_JEXEC' ) or die( 'Restricted access' ); 


class MedsignalModelsDefault extends JModelBase
{
  protected $__state_set  = null;
  protected $_total       = null;
  protected $_pagination  = null;
  protected $_db          = null;
  protected $id           = null;
  protected $limitstart   = 0;
  protected $limit        = 10;
 
  function __construct()
  {

    parent::__construct(); 
  }

  public function store($data=null)
  {    
    $data = $data ? $data : JRequest::get('post');
    $row = JTable::getInstance($data['table'],'Table');

    $date = date("Y-m-d H:i:s");

     // Bind the form fields to the table
    if (!$row->bind($data))
    {
        return false;
    }

    $row->modified = $date;
    if ( !$row->created )
    {
      $row->created = $date;
    }

    // Make sure the record is valid
    if (!$row->check())
    {
        return false;
    }
 
    if (!$row->store())
    {
        return false;
    }

    return $row;

  }
}

<?php defined( '_JEXEC' ) or die( 'Restricted access' ); 
 
class TableItem extends JTable
{                      
  /**
  * Constructor
  *
  * @param object Database connector object
  */
  function __construct( &$db ) {
    parent::__construct('#__medsignal_item', 'item_id', $db);
  }
}

JTable::addIncludePath(JPATH_COMPONENT_ADMINISTRATOR . '/tables'); 

$row = JTable::getInstance('Item', 'Table'); 

[quote author=broadcast77 link=topic=318347.msg1585476#msg1585476 date=1442792498]
  	 $model = new $modelName();
   	if ( $row = $model->store() )

JTable::addIncludePath(JPATH_COMPONENT_ADMINISTRATOR . '/tables');

1054 Unknown column 'modified' in 'field list' SQL=INSERT INTO `efy0h_medsignal_item` (`item_name`,`item_price`,`modified`,`created`) VALUES ('sdf','sdf','2015-09-21 12:30:45','2015-09-21 12:30:45')

<form id="itemForm">
    <input type="hidden" name="table" value="item">
    <input type="text" name="item_name" placeholder="укажите название"> 
    <input type="text" name="item_artikul" placeholder="укажите артикул"> 
    <input type="text" name="item_price" placeholder="укажите цену">
    <input type="text" name="item_quant" placeholder="укажите количество">
	<input type="button" value="загрузить товар" onclick="addNewItem()">
</form>

$row->modified = $date;
    if ( !$row->created )
    {
      $row->created = $date;
    }