if (control.getBackButtonNode() != null && control.getNextButtonNode() != null) { control.getBackButtonNode().setOnMouseClicked(backButtonEventHandler); control.getNextButtonNode().setOnMouseClicked(nextButtonEventHandler); control.getBackButtonNode().hoverProperty().addListener(changeListenerBack); control.getNextButtonNode().hoverProperty().addListener(changeListenerNext); } else {