a php error was encountered in grocery_crud

Question

I'm trying to install groceryCRUD. I've already successfully installed code igniter but when I try to access /index.php/examples are displayed many errors such as:

<h4>A PHP Error was encountered</h4>

<p>Severity: Notice</p>
<p>Message:  Undefined property: stdClass::$</p>
<p>Filename: libraries/Grocery_CRUD.php</p>
<p>Line Number: 1612</p>

</div><div style="border:1px solid #990000;padding-left:20px;margin:0 0 10px 0;">

<h4>A PHP Error was encountered</h4>

<p>Severity: Notice</p>
<p>Message:  Undefined property: stdClass::$</p>
<p>Filename: libraries/Grocery_CRUD.php</p>
<p>Line Number: 1613</p>

</div><div style="border:1px solid #990000;padding-left:20px;margin:0 0 10px 0;">

<h4>A PHP Error was encountered</h4>

<p>Severity: Notice</p>
<p>Message:  Undefined property: stdClass::$</p>
<p>Filename: libraries/Grocery_CRUD.php</p>
<p>Line Number: 1614</p>

</div><div style="border:1px solid #990000;padding-left:20px;margin:0 0 10px 0;">

<h4>A PHP Error was encountered</h4>

<p>Severity: Notice</p>
<p>Message:  Undefined property: stdClass::$</p>
<p>Filename: libraries/Grocery_CRUD.php</p>
<p>Line Number: 1615</p>

this line number error code:

foreach($data->list as $num_row => $row)
{
    $data->list[$num_row]->primary_key_value = $row->{$data->primary_key};
    $data->list[$num_row]->edit_url = $data->edit_url.'/'.$row->{$data->primary_key};
    $data->list[$num_row]->delete_url = $data->delete_url.'/'.$row->{$data->primary_key};
    $data->list[$num_row]->read_url = $data->read_url.'/'.$row->{$data->primary_key};
}

Can someone please help me fixing bugs? thank you.