Using rewrite-user-name-regex element in Elytron client configuration file causes NPE

java.lang.NullPointerException
org.wildfly.security.auth.client.AuthenticationConfiguration.rewriteUser(AuthenticationConfiguration.java:492)
org.wildfly.security.auth.client.ElytronXmlParser.lambda$parseAuthenticationConfigurationType$14(ElytronXmlParser.java:605)
org.wildfly.security.auth.client.ElytronXmlParser.lambda$andThenOp$27(ElytronXmlParser.java:832)
org.wildfly.security.auth.client.ElytronXmlParser.lambda$andThenOp$27(ElytronXmlParser.java:832)
org.wildfly.security.auth.client.ElytronXmlParser.lambda$andThenOp$27(ElytronXmlParser.java:832)
org.wildfly.security.auth.client.ElytronXmlParser.lambda$parseAuthenticationConfigurationType$25(ElytronXmlParser.java:704)
org.wildfly.security.auth.client.ElytronXmlParser.lambda$parseAuthenticationRuleType$7(ElytronXmlParser.java:513)
org.wildfly.security.auth.client.ElytronXmlParser.lambda$parseRulesType$8(ElytronXmlParser.java:537)
org.wildfly.security.auth.client.ElytronXmlParser.parseAuthenticationClientType(ElytronXmlParser.java:308)
org.wildfly.security.auth.client.ElytronXmlParser.parseAuthenticationClientConfiguration(ElytronXmlParser.java:180)
org.wildfly.security.auth.client.ElytronXmlParser.parseAuthenticationClientConfiguration(ElytronXmlParser.java:141)
com.redhat.eap.qe.elytron.authnctx.WildflyConfigXmlServlet.parseAndCreateAuthenticationClientConfiguration(WildflyConfigXmlServlet.java:120)
com.redhat.eap.qe.elytron.authnctx.WildflyConfigXmlServlet.doGet(WildflyConfigXmlServlet.java:95)
javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85)
io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
org.wildfly.extension.undertow.deployment.GlobalRequestControllerHandler.handleRequest(GlobalRequestControllerHandler.java:68)
io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:292)
io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:81)
io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:138)
io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:135)
io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
org.wildfly.extension.undertow.security.SecurityContextThreadSetupAction.lambda$create$0(SecurityContextThreadSetupAction.java:105)
org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1704)
org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1704)
org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1704)
org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1704)
io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:272)
io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:104)
io.undertow.server.Connectors.executeRootHandler(Connectors.java:211)
io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:809)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
java.lang.Thread.run(Thread.java:745)