Undefined index: shipping_rates in commerce_shipping_pane_checkout_form_validate()

I can confirm this patch does what it says, but since I'm working on the same project as citlacom, will leave it to someone else to also verify.

I actually don't have this problem. We do define this variable whether there are services or not in the form builder:

  $pane_form['shipping_rates'] = array(
    '#type' => 'value',
    '#value' => FALSE,
  );

My hunch is you have an alteration or something that's interfering with the code from working; or it's just something that's beyond me. That said, I prefer empty() checks to using a mixed type variable as a boolean. I'll update the validate handler to use that. : )