Group search page in Keycloak fails with error: "b.map is not a function"

Issue

• After making modifications to group mapper, Groups tab gives an error, 'b.map is not a function' on initial access

• Logs show following error from "GroupsResource.listGroups" call:

  ERROR [org.keycloak.services.error.KeycloakErrorHandler] (executor-thread-495) Uncaught server error: java.lang.NullPointerException: Cannot invoke "java.lang.Comparable.compareTo(Object)" because the return value of "java.util.function.Function.apply(Object)" is null