500 Servlet Exception

java.lang.NumberFormatException: null
	at java.lang.Integer.parseInt(Integer.java:454)
	at java.lang.Integer.parseInt(Integer.java:527)
	at Contador.setPath(Contador.java:87)
	at _global__jsp._jspService(/global.jsp:11)
	at com.caucho.jsp.JavaPage.service(JavaPage.java:75)
	at com.caucho.jsp.Page.subservice(Page.java:506)
	at com.caucho.server.http.FilterChainPage.doFilter(FilterChainPage.java:182)
	at com.caucho.server.http.Invocation.service(Invocation.java:315)
	at com.caucho.server.http.CacheInvocation.service(CacheInvocation.java:135)
	at com.caucho.server.http.QRequestDispatcher.include(QRequestDispatcher.java:362)
	at com.caucho.server.http.QRequestDispatcher.include(QRequestDispatcher.java:274)
	at com.caucho.jsp.QPageContext.include(QPageContext.java:547)
	at _index__jsp._jspService(_index__jsp.java:27)
	at com.caucho.jsp.JavaPage.service(JavaPage.java:75)
	at com.caucho.jsp.Page.subservice(Page.java:506)
	at com.caucho.server.http.FilterChainPage.doFilter(FilterChainPage.java:182)
	at com.caucho.server.http.Invocation.service(Invocation.java:315)
	at com.caucho.server.http.CacheInvocation.service(CacheInvocation.java:135)
	at com.caucho.server.http.HttpRequest.handleRequest(HttpRequest.java:246)
	at com.caucho.server.http.HttpRequest.handleConnection(HttpRequest.java:163)
	at com.caucho.server.TcpConnection.run(TcpConnection.java:139)
	at java.lang.Thread.run(Thread.java:745)

Resin 2.1.11 (built Mon Sep 8 09:36:19 PDT 2003)