RealmBase->findSecurityConstraints throws NPE

When you deploy the attached web application, you will see a NPE as follows:

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20:01:06,311 ERROR [CoyoteAdapter] An exception or error occurred in the container during the request processing
java.lang.NullPointerException
at org.apache.catalina.realm.RealmBase.findSecurityConstraints(RealmBase.java:502)
at org.jboss.web.tomcat.security.JBossWebRealm.findSecurityConstraints(JBossWebRealm.java:459)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:426)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:92)
at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.process(SecurityContextEstablishmentValve.java:126)
at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:70)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:330)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:829)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:601)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:595)
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The line that is failing in RealmBase is:
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// Check each defined security constraint
String uri = request.getRequestPathMB().toString();
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after this line, the url becomes null.