fix getRootNodeName return

[rushork]

A fix for the problem first raised in #871.

This return from the getRootNodeName function was incorrectly deleted in #801, making it unable to save TrackingOptions correctly e.g. the following way:

  $option = new TrackingOption();
  $option->setName($name);
  $tracking->addOption($option);
  $tracking->save();

The suggested change is to reinstate what it was previously and allow TrackingOptions to be saved properly. Interestingly, it seems to allow one TrackingOption to be generated but I try to add another to the same Tracking Category it does not save.