InfoPath Dev

Hi. I have the following code:

                    objRoot = objXnDoc.SelectSingleNode("/my:AddFloor/my:rtbBuildingsInUseGr1/my:rtbBuildingsInUseGr2/my:listBuildings", NamespaceManager);
                    if (objRoot.Value != "")
                    {
                        objRoot.DeleteSelf();
                    }
                    else
                    {
                        return;
                    }

and I get this error when there are no more lines to delete:

NullReferenceException was unhadlet by the user code.

Why? Thank you!

 How do i bypass it?

 I have managed to bypass it by using try and catch, but I still want to know if there is another way to bypas it. Thank you!

try catch would be it - makes sense - if there's no apples, and someone told me to eat the apple, i might have an error too ;-)