500 Servlet Exception

java.lang.StringIndexOutOfBoundsException: String index out of range: -1
	at java.lang.String.substring(String.java:1444)
	at com.thalia.common.SourceCodeTool.mixString(Unknown Source)
	at _jsp._product._product_0info__jsp._jspService(product/product_info.jsp:576)
	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.thalia.sys.SysAccessLogFilter.doFilter(Unknown Source)
	at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
	at com.caucho.filters.RewriteFilter.doFilter(RewriteFilter.java:120)
	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:534)