Array To String error / undefined $query

There are various ways to solve this.
One way is introducing a 3rd parameter for the render function, e.g.:

PHP Code:

protected function render($the_view = NULL, $template = 'master', $data = NULL )
{
   if ($data) $this->data = $data;
  //etc.
} 


From you controller, call the function with the 3 parameters:

PHP Code:

$this->render('admin/docs/existing_view', NULL, $data); 


But remember to check all calls to the render function in all your controllers.