login page hangs

Mandy reports: if one browses to Demo.dataverse.org > click Sign Up > click other login options > click Username/Email > enter account credentials/pw > click Log In button > Demo Dataverse hangs.

https://user-images.githubusercontent.com/12831666/154521378-90892e12-aaf8-40cd-b3c6-b6026c177ace.mp4

I've reproduced this in Firefox on Windows and in Chrome on a Mac. On a test 5.3 instance it throws:

  #{DataverseUserPage.init}: java.lang.NullPointerException
javax.faces.FacesException: #{DataverseUserPage.init}: java.lang.NullPointerException
        at com.sun.faces.application.ActionListenerImpl.getNavigationOutcome(ActionListenerImpl.java:96)
        at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:71)
Caused by: javax.faces.el.EvaluationException: java.lang.NullPointerException
        at com.sun.faces.application.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:76)
        at com.sun.faces.application.ActionListenerImpl.getNavigationOutcome(ActionListenerImpl.java:82)
        ... 45 more
Caused by: java.lang.NullPointerException
        at edu.harvard.iq.dataverse.authorization.providers.builtin.DataverseUserPage.init(DataverseUserPage.java:170)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  StandardWrapperValve[Faces Servlet]: Servlet.service() for servlet Faces Servlet threw exception
java.lang.NullPointerException
        at edu.harvard.iq.dataverse.authorization.providers.builtin.DataverseUserPage.init(DataverseUserPage.java:170)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

Reproduce the Sign Up > other login options > Username/Email flow described in the issue, then inspect edu.harvard.iq.dataverse.authorization.providers.builtin.DataverseUserPage.init at DataverseUserPage.java:170 alongside the reported stack trace. Done means the Username/Email login no longer hangs or throws the reported NullPointerException.