Call to a member function event() on null

Need Help
1

Hi,
I am migrate my cakephp1.3 to 2.9 and I am rename ajax helper to AjaxHelper and javascript helper to JavascriptHelper.i want to used same helper in my form section.
Form is working fine.But the problem is when I sent Ajax request in AjaxHepler file its give the error “Call to a member function event() on null”.
Please help I want to used same helper in my application.