500 error in struts 2.0 login application

[Vishwas Tyagi]

hi to all, i am making a simple login application
when i run my simple login application i get error
my simple login application takes username and password from user on login.jsp page ,validate it in Action class and open, the adminhome.jsp page on sucess and invalid.jsp page on failure using struts.xml.
i used titles(2.0.1) in adminhome.jsp by the help of tiles.xml
when i make request of login.jsp page from browser it shows this error.

Error 500--Internal Server Error
java.lang.NullPointerException
at org.apache.struts2.views.jsp.TagUtils.getStack(TagUtils.java:58)
at org.apache.struts2.views.jsp.StrutsBodyTagSupport.getStack(StrutsBodyTagSupport.java:54)
at org.apache.struts2.views.jsp.ComponentTagSupport.doStartTag(ComponentTagSupport.java:49)
at jsp_servlet.__login._jsp__tag0(__login.java:116)
at jsp_servlet.__login._jspService(__login.java:87)
at weblogic.servlet.jsp.JspBase.service(JspBase.java:34)
at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227)
at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125)
at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:292)
at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:175)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3495)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
at weblogic.security.service.SecurityManager.runAs(Unknown Source)
at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2180)
at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2086)
at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1406)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:201)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:173)








i have also cheked FAQ but that did not assist me.
Please help if anyone know answer.
Immediate help required.