org.apache.solr.servlet.HttpSolrCall.getAuthCtx().new AuthorizationContext() {...}.getParams() sometimes throw java.lang.NullPointerException

Sometimes solrReq in HttpSolrCall is null, causing a NullPointerException. See the following log:

2017-05-08 16:05:30,221 ERROR org.apache.solr.servlet.HttpSolrCall: null:java.lang.NullPointerException
at org.apache.solr.servlet.HttpSolrCall$2.toString(HttpSolrCall.java:1001)
at java.lang.String.valueOf(String.java:2854)
at java.lang.StringBuilder.append(StringBuilder.java:128)
at org.apache.ranger.authorization.solr.authorizer.RangerSolrAuthorizer.authorize(RangerSolrAuthorizer.java:231)
at org.apache.ranger.authorization.solr.authorizer.RangerSolrAuthorizer.authorize(RangerSolrAuthorizer.java:128)
at org.apache.solr.servlet.HttpSolrCall.call(HttpSolrCall.java:422)
at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:279)
at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:230)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:745)