VelocityServlet: Error processing the template

For input string: "null"
java.lang.NumberFormatException: For input string: "null"
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
	at java.lang.Integer.parseInt(Integer.java:468)
	at java.lang.Integer.parseInt(Integer.java:518)
	at com.palmerparker.site.HouseDetails.handleAndTemplate(HouseDetails.java:64)
	at com.palmerparker.site.HouseSearchServlet.handleRequest(HouseSearchServlet.java:38)
	at org.apache.velocity.servlet.VelocityServlet.doRequest(VelocityServlet.java:358)
	at org.apache.velocity.servlet.VelocityServlet.doGet(VelocityServlet.java:317)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:748)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
	at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
	at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
	at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
	at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
	at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2417)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
	at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
	at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
	at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
	at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
	at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
	at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
	at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
	at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:193)
	at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:309)
	at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:387)
	at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:673)
	at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:615)
	at org.apache.jk.common.SocketConnection.runIt(ChannelSocket.java:786)
	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:666)
	at java.lang.Thread.run(Thread.java:552)