RH-SSO client throws exception "Failed to enforce policy decisions"

Issue

• Authenticated API calls fail with unclear error

• Exception stack trace is application server has error

  java.lang.RuntimeException: Failed to enforce policy decisions.
          at org.keycloak.adapters.AuthenticatedActionsHandler.isAuthorized(AuthenticatedActionsHandler.java:168)[321:org.keycloak.keycloak-adapter-core:4.8.3.Final-redhat-00001]
          at org.keycloak.adapters.AuthenticatedActionsHandler.handledRequest(AuthenticatedActionsHandler.java:60)
  ...
  Caused by: org.keycloak.authorization.client.util.HttpResponseException: Unexpected response from server: 500 / Internal Server Error / Response from server: {"error":"server_error","error_description":"Unexpected error while evaluating permissions"}
      at org.keycloak.authorization.client.util.HttpMethod.execute(HttpMethod.java:95)[323:org.keycloak.keycloak-authz-client:4.8.3.Final-redhat-00001]
      at org.keycloak.authorization.client.util.HttpMethodResponse$2.execute(HttpMethodResponse.java:50)[323:org.keycloak.keycloak-authz-client:4.8.3.Final-redhat-00001]
      at org.keycloak.authorization.client.resource.AuthorizationResource$1.call(AuthorizationResource.java:90)[323:org.keycloak.keycloak-authz-client:4.8.3.Final-redhat-00001]
      at org.keycloak.authorization.client.resource.AuthorizationResource$1.call(AuthorizationResource.java:74)[323:org.keycloak.keycloak-authz-client:4.8.3.Final-redhat-00001]
      at org.keycloak.authorization.client.resource.AuthorizationResource.authorize(AuthorizationResource.java:94)[323:org.keycloak.keycloak-authz-client:4.8.3.Final-redhat-00001]
      ... 24 more
  

• RH-SSO server has exception ending with:

  Caused by: java.lang.NullPointerException
      at org.keycloak.authorization.common.KeycloakIdentity.<init>(KeycloakIdentity.java:128)
      ... 76 more