VelocityServlet : Error processing the template

java.lang.NullPointerException
java.lang.NullPointerException
	at uk.org.tate.bean.collections.DisplayHelper.findShowByPrimaryKey(DisplayHelper.java:253)
	at uk.org.tate.bean.collections.DisplayHome.getDisplayShow(DisplayHome.java:173)
	at uk.org.tate.bean.collections.DisplayRoomBean.getShow(DisplayRoomBean.java:151)
	at uk.org.tate.application.collections.CollectionDisplays.handleRequest(CollectionDisplays.java:85)
	at org.apache.velocity.servlet.VelocityServlet.doRequest(VelocityServlet.java:372)
	at uk.org.tate.core.servlet.TateServlet.doRequest(TateServlet.java:305)
	at org.apache.velocity.servlet.VelocityServlet.doGet(VelocityServlet.java:333)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
	at org.apache.catalina.servlets.InvokerServlet.serveRequest(InvokerServlet.java:419)
	at org.apache.catalina.servlets.InvokerServlet.doGet(InvokerServlet.java:133)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
	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.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:118)
	at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:52)
	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:204)
	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.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
	at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:199)
	at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:282)
	at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:754)
	at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:684)
	at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:876)
	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
	at java.lang.Thread.run(Thread.java:619)