Trying to get property of non-object

[eluser]Ram Krishna[/eluser]
this code is written in model .it is giving error

A PHP Error was encountered

Severity: Notice

Message: Trying to get property of non-object

Filename: models/user.php

Line Number: 30


the line number 30 is the code written inside foreach loop.

Code:

function country()
{
  

  $this->db->select('id,country_name');
  $query=$this->db->get('countries');
  $data=array();
  foreach($query->result_array() as $row)
  {
   $data[$row->id]=$row->country_name;
  }
  return ($data);
}

Please help me.