500 Servlet Exception

javax.servlet.jsp.JspException: ServletException in '/WEB-INF/jsp/skins/zoomjam/layout/homepageLayout.jsp':
ServletException in '/WEB-INF/jsp/skins/zoomjam/games/homepage/homepage_content.jsp':
Define tag cannot set a null value
	at org.apache.struts.taglib.tiles.InsertTag$InsertHandler.doEndTag(InsertTag.java:921)
	at org.apache.struts.taglib.tiles.InsertTag.doEndTag(InsertTag.java:460)
	at _jsp._WEB_22dINF._jsp._pages._homepage._homepage__jsp._jspService(WEB-INF/jsp/pages/homepage/homepage.jsp:43)
	at com.caucho.jsp.JavaPage.service(JavaPage.java:60)
	at com.caucho.jsp.Page.pageservice(Page.java:570)
	at com.caucho.server.dispatch.PageFilterChain.doFilter(PageFilterChain.java:179)
	at com.caucho.server.webapp.DispatchFilterChain.doFilter(DispatchFilterChain.java:115)
	at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:229)
	at com.caucho.server.webapp.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:277)
	at com.caucho.server.webapp.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:106)
	at org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1056)
	at org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:388)
	at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:231)
	at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1164)
	at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:397)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:115)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:92)
	at com.caucho.server.dispatch.ServletFilterChain.doFilter(ServletFilterChain.java:106)
	at com.systemsnets.skillgames.web.filters.SystemFilter.doFilter(SystemFilter.java:135)
	at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
	at org.springframework.orm.hibernate.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:174)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
	at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
	at com.systemsnets.skillgames.web.filters.CharsetFilter.doFilter(CharsetFilter.java:26)
	at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
	at com.systemsnets.skillgames.web.filters.PerformanceLoggingFilter.doFilterInternal(PerformanceLoggingFilter.java:26)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
	at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
	at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:173)
	at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:229)
	at com.caucho.server.hmux.HmuxRequest.handleRequest(HmuxRequest.java:420)
	at com.caucho.server.port.TcpConnection.run(TcpConnection.java:511)
	at com.caucho.util.ThreadPool.runTasks(ThreadPool.java:520)
	at com.caucho.util.ThreadPool.run(ThreadPool.java:442)
	at java.lang.Thread.run(Thread.java:619)