[purge, NullPointer] invoking purge intermittently throws a NullPointer

java.lang.NullPointerException
             at org.apache.activemq.broker.region.Queue.doPageIn(Queue.java:1894)
             at org.apache.activemq.broker.region.Queue.purge(Queue.java:1246)
             at org.apache.activemq.broker.jmx.QueueView.purge(QueueView.java:62)
             at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
             at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
             at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
             at java.lang.reflect.Method.invoke(Method.java:498)
             at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
             at sun.reflect.GeneratedMethodAccessor24.invoke(Unknown Source)
             at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
             at java.lang.reflect.Method.invoke(Method.java:498)
             at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
             at com.sun.jmx.mbeanserver.StandardMBeanIntrospector.invokeM2(StandardMBeanIntrospector.java:112)
             at com.sun.jmx.mbeanserver.StandardMBeanIntrospector.invokeM2(StandardMBeanIntrospector.java:46)
             at com.sun.jmx.mbeanserver.MBeanIntrospector.invokeM(MBeanIntrospector.java:237)
             at com.sun.jmx.mbeanserver.PerInterface.invoke(PerInterface.java:138)
             at com.sun.jmx.mbeanserver.MBeanSupport.invoke(MBeanSupport.java:252)
             at javax.management.StandardMBean.invoke(StandardMBean.java:405)
             at org.apache.activemq.broker.jmx.AnnotatedMBean.invoke(AnnotatedMBean.java:238)
             at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
             at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
             at org.jolokia.handler.ExecHandler.doHandleRequest(ExecHandler.java:98)
             at org.jolokia.handler.ExecHandler.doHandleRequest(ExecHandler.java:40)
             at org.jolokia.handler.JsonRequestHandler.handleRequest(JsonRequestHandler.java:89)
             at org.jolokia.backend.MBeanServerExecutorLocal.handleRequest(MBeanServerExecutorLocal.java:109)
             at org.jolokia.backend.MBeanServerHandler.dispatchRequest(MBeanServerHandler.java:161)
             at org.jolokia.backend.LocalRequestDispatcher.dispatchRequest(LocalRequestDispatcher.java:99)
             at org.jolokia.backend.BackendManager.callRequestDispatcher(BackendManager.java:413)
             at org.jolokia.backend.BackendManager.handleRequest(BackendManager.java:158)
             at org.jolokia.http.HttpRequestHandler.executeRequest(HttpRequestHandler.java:197)
             at org.jolokia.http.HttpRequestHandler.handlePostRequest(HttpRequestHandler.java:137)
             at org.jolokia.jvmagent.handler.JolokiaHttpHandler.executePostRequest(JolokiaHttpHandler.java:279)
             at org.jolokia.jvmagent.handler.JolokiaHttpHandler.doHandle(JolokiaHttpHandler.java:233)
             at org.jolokia.jvmagent.handler.JolokiaHttpHandler.handle(JolokiaHttpHandler.java:178)
             at com.sun.net.httpserver.Filter$Chain.doFilter(Filter.java:79)
             at sun.net.httpserver.AuthFilter.doFilter(AuthFilter.java:72)
             at com.sun.net.httpserver.Filter$Chain.doFilter(Filter.java:82)
             at sun.net.httpserver.ServerImpl$Exchange$LinkHandler.handle(ServerImpl.java:675)
             at com.sun.net.httpserver.Filter$Chain.doFilter(Filter.java:79)
             at sun.net.httpserver.ServerImpl$Exchange.run(ServerImpl.java:645)
             at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
             at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
             at java.lang.Thread.run(Thread.java:748)