"Variable data seems to be uninitialized" - Netbeans warning message

[eluser]term25[/eluser]
NetBeans is throwing this warning message:
Variable $data seems to be uninitialized

In this code:

Code:

public function services()
{
    $data['header'] = "Services";
    $this->load->view('admin_services_view', $data);
}

What does warning message mean? Should I write it like this and why?

Code:

public function services($data)
{
    $data['header'] = "Services";
    $this->load->view('admin_services_view', $data);
}

Or is the problem somewhere else? Thanks in advance.