Glidewindow catalog client script Onload not working on service portal

hi All,

I have created a catalog client script on Load using glidewindow. When i tested on Portal it is triggering the Java console error. Kindly help

function onLoad() {

var dialog = new GlideDialogWindow('EAP_popup');
dialog.setTitle(new GwtMessage().getMessage('Confirmation'));
dialog.setSize(750,1000); 
dialog.removeCloseDecoration(); //Remove the dialog close icon
dialog.setPreference('cancel_url', '/google.com');
dialog.render();
}