NPE when directly accessing authenticationendpoint/oauth_error

[hauntingEcho]

Description:
when trying to navigate directly to authenticationendpoint/oauth2_error.do on a local installation of wso2 IS 5.7.0, an unthemed error page is shown (which appears to be samlsso_notification.jsp with the null statusMessage behavior) and the following is printed to the console:

[2018-09-05 15:07:55,499] ERROR {org.apache.catalina.core.StandardWrapperValve} -  Servlet.service() for servlet [oauth2_error.do] in context with path [/authenticationendpoint] threw exception [An exception occurred processing JSP page /oauth2_error.jsp at line 29

26:     String regex = "application=";
27:     String errorMsgContext = errorMsg;
28:     String errorMsgApp = "";
29:     String[] error = errorMsg.split(regex);
30:     if (error.length > 1) {
31:         errorMsgContext = errorMsg.split(regex)[0] + regex;
32:         errorMsgApp = errorMsg.split(regex)[1];


Stacktrace:] with root cause
java.lang.NullPointerException
	at org.apache.jsp.oauth2_005ferror_jsp._jspService(oauth2_005ferror_jsp.java:134)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.wso2.carbon.ui.filters.cache.ContentTypeBasedCachePreventionFilter.doFilter(ContentTypeBasedCachePreventionFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.wso2.carbon.identity.application.authentication.endpoint.util.filter.AuthenticationEndpointFilter.doFilter(AuthenticationEndpointFilter.java:165)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.catalina.filters.HttpHeaderSecurityFilter.doFilter(HttpHeaderSecurityFilter.java:124)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
	at org.wso2.carbon.identity.context.rewrite.valve.TenantContextRewriteValve.invoke(TenantContextRewriteValve.java:80)
	at org.wso2.carbon.identity.authz.valve.AuthorizationValve.invoke(AuthorizationValve.java:91)
	at org.wso2.carbon.identity.auth.valve.AuthenticationValve.invoke(AuthenticationValve.java:60)
	at org.wso2.carbon.tomcat.ext.valves.CompositeValve.continueInvocation(CompositeValve.java:99)
	at org.wso2.carbon.tomcat.ext.valves.CarbonTomcatValve$1.invoke(CarbonTomcatValve.java:47)
	at org.wso2.carbon.webapp.mgt.TenantLazyLoaderValve.invoke(TenantLazyLoaderValve.java:57)
	at org.wso2.carbon.tomcat.ext.valves.TomcatValveContainer.invokeValves(TomcatValveContainer.java:47)
	at org.wso2.carbon.tomcat.ext.valves.CompositeValve.invoke(CompositeValve.java:62)
	at org.wso2.carbon.tomcat.ext.valves.CarbonStuckThreadDetectionValve.invoke(CarbonStuckThreadDetectionValve.java:159)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)
	at org.wso2.carbon.tomcat.ext.valves.CarbonContextCreatorValve.invoke(CarbonContextCreatorValve.java:57)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1115)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1775)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1734)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:745)

Suggested Labels:
Complexity/Low (needs a default behavior when the request parameters are null), Type/Bug

Affected Product Version:
5.11.256, IS 5.7.0, master branch

Steps to reproduce:

1. start local instance of WSO2 IS 5.7.0
2. go to http://localhost:9443/authenticationendpoint/oauth2_error.do
3. check console output

Related Issues:
wso2/product-is#3690