java.lang.NullPointerException: Cannot get property 'controller' on null object

Question

I am using the Jenkins-as-a-Configuration tool to launch my Jenkins server but when I port-forward to my local host on port 8080 and try accessing the server, I am greeted with the error java.lang.NullPointerException: Cannot get property 'controller' on null object. Not sure why this is suddenly happening as I have been able to access it prior.