You should use
SceneBuilder 2 and it's associated
getting started guide, rather than the dated SceneBuilder 1 getting started guide.
The error you are getting:
means that you are trying to reference a some object on line 481 of IssueTrackingLiteController.java and that object has not been initialized to some value.
I don't know what that object is, so I couldn't tell you why it is not initialized.
A likely candidates is a mismatch between an fx:id name definition and an @FXML marked variable name in your controller class, which prevented correct initialization of the object (but that is just a guess).