500 Servlet Exception

java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 0
	at java.util.Vector.get(Vector.java:694)
	at _jsp._question._paform__jsp._jspService(question/paform.jsp:228)
	at com.caucho.jsp.JavaPage.service(JavaPage.java:61)
	at com.caucho.jsp.Page.pageservice(Page.java:578)
	at com.caucho.server.dispatch.PageFilterChain.doFilter(PageFilterChain.java:192)
	at com.caucho.server.webapp.DispatchFilterChain.doFilter(DispatchFilterChain.java:97)
	at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:241)
	at com.caucho.server.webapp.RequestDispatcherImpl.include(RequestDispatcherImpl.java:491)
	at com.caucho.server.webapp.RequestDispatcherImpl.include(RequestDispatcherImpl.java:355)
	at com.caucho.jsp.PageContextImpl.include(PageContextImpl.java:1002)
	at _jsp._ses._mainSESQuestion__jsp._jspService(ses/mainSESQuestion.jsp:31)
	at com.caucho.jsp.JavaPage.service(JavaPage.java:61)
	at com.caucho.jsp.Page.pageservice(Page.java:578)
	at com.caucho.server.dispatch.PageFilterChain.doFilter(PageFilterChain.java:192)
	at com.caucho.server.webapp.DispatchFilterChain.doFilter(DispatchFilterChain.java:97)
	at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:241)
	at com.caucho.server.webapp.RequestDispatcherImpl.include(RequestDispatcherImpl.java:491)
	at com.caucho.server.webapp.RequestDispatcherImpl.include(RequestDispatcherImpl.java:355)
	at com.caucho.jsp.PageContextImpl.include(PageContextImpl.java:1002)
	at _jsp._ses._mainHome__jsp._jspService(ses/mainHome.jsp:2)
	at com.caucho.jsp.JavaPage.service(JavaPage.java:61)
	at com.caucho.jsp.Page.pageservice(Page.java:578)
	at com.caucho.server.dispatch.PageFilterChain.doFilter(PageFilterChain.java:192)
	at com.caucho.server.webapp.DispatchFilterChain.doFilter(DispatchFilterChain.java:97)
	at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:241)
	at com.caucho.server.webapp.RequestDispatcherImpl.include(RequestDispatcherImpl.java:491)
	at com.caucho.server.webapp.RequestDispatcherImpl.include(RequestDispatcherImpl.java:355)
	at com.caucho.jsp.PageContextImpl.include(PageContextImpl.java:1002)
	at _jsp._ses._index__jsp._jspService(ses/index.jsp:10)
	at com.caucho.jsp.JavaPage.service(JavaPage.java:61)
	at com.caucho.jsp.Page.pageservice(Page.java:578)
	at com.caucho.server.dispatch.PageFilterChain.doFilter(PageFilterChain.java:192)
	at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:178)
	at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:241)
	at com.caucho.server.hmux.HmuxRequest.handleRequest(HmuxRequest.java:435)
	at com.caucho.server.port.TcpConnection.run(TcpConnection.java:586)
	at com.caucho.util.ThreadPool$Item.runTasks(ThreadPool.java:690)
	at com.caucho.util.ThreadPool$Item.run(ThreadPool.java:612)
	at java.lang.Thread.run(Thread.java:619)