SPNEGO test with jboss-negotiation-tookit getting a NullPointerException from RealmDirectLoginModule

Issue

• Followed instructions in How to Set Up SSO for JBoss EAP with Kerberos guide but getting a NullPointerException with default JBoss Negotiation Toolkit

• Testing Kerberos, or SPNEGO, with boss-negotiation-toolkit configuration with Elytron is giving the following error:

  2020-06-09 12:40:43,244 ERROR [org.jboss.security.negotiation.toolkit.SecurityDomainTestServlet] (default task-12) testDomain Failed: javax.security.auth.login.LoginException: java.lang.NullPointerException
          at org.jboss.as.security.RealmDirectLoginModule.getDigestCredential(RealmDirectLoginModule.java:250)
          at org.jboss.as.security.RealmDirectLoginModule.login(RealmDirectLoginModule.java:149)
          ....
          at javax.security.auth.login.LoginContext.login(LoginContext.java:587)
          at org.jboss.security.negotiation.toolkit.SecurityDomainTestServlet.testDomain(SecurityDomainTestServlet.java:108)