The error message pasted below is displayed after I performed the following steps:
Open Project Role Browser
Click on View Usage for role Administrators
Select click on View for a Permission Scheme
Click on Edit in column users for Role Administrators

Error Message:
An error occurred whilst rendering this message. Please contact the administrators, and inform them of this bug. Details: ------- java.lang.NullPointerException at org.apache.velocity.context.InternalContextAdapterImpl.get(InternalContextAdapterImpl.java:162) at org.apache.velocity.runtime.parser.node.ASTReference.getVariableValue(ASTReference.java:623) at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:151) at org.apache.velocity.runtime.parser.node.ASTReference.evaluate(ASTReference.java:307) at org.apache.velocity.runtime.parser.node.ASTExpression.evaluate(ASTExpression.java:45) at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:68) at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:230) at org.apache.velocity.Template.merge(Template.java:256) at org.apache.velocity.app.VelocityEngine.mergeTemplate(VelocityEngine.java:450) at com.atlassian.velocity.DefaultVelocityManager.getEncodedBody(DefaultVelocityManager.java:76) at com.atlassian.jira.plugin.webwork.JiraPluginWebworkVelocityServlet.service(JiraPluginWebworkVelocityServlet.java:48) at javax.servlet.http.HttpServlet.service(HttpServlet.java:802) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:672) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:463) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:398) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301) at com.atlassian.jira.web.dispatcher.JiraServletDispatcher.service(JiraServletDispatcher.java:279) at javax.servlet.http.HttpServlet.service(HttpServlet.java:802) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.jira.web.filters.AccessLogFilter.doFilter(AccessLogFilter.java:51) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:119) at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:55) at com.atlassian.jira.web.filters.SitemeshExcludePathFilter.doFilter(SitemeshExcludePathFilter.java:38) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:182) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:181) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(ProfilingFilter.java:132) at com.atlassian.jira.web.filters.JIRAProfilingFilter.doFilter(JIRAProfilingFilter.java:16) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.jira.web.filters.ActionCleanupDelayFilter.doFilter(ActionCleanupDelayFilter.java:41) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.jira.web.filters.RequestCleanupFilter.doFilter(RequestCleanupFilter.java:49) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.johnson.filters.JohnsonFilter.doFilter(JohnsonFilter.java:91) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.jira.web.filters.gzip.GzipFilter.doFilter(GzipFilter.java:72) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.core.filters.AbstractEncodingFilter.doFilter(AbstractEncodingFilter.java:37) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.jira.appconsistency.db.DatabaseCompatibilityEnforcerFilter.doFilter(DatabaseCompatibilityEnforcerFilter.java:25) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:541) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869) at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684) at java.lang.Thread.run(Thread.java:595)