sitemesh当include页面用了自定义标签后有异常，求助。

你好！
    我sitemesh的主页面body体如下：
         <body>
<%@include file="header.jsp" %>
<decorator:body />
<%@include file="footer.jsp" %>
</body>
当header.jsp中使用了自定义标签后就会有异常（注：标签没有问题，因为标签在），如下：
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java.lang.NullPointerException
at org.apache.struts2.views.jsp.ComponentTagSupport.doStartTag(ComponentTagSupport.java:49)
at org.apache.jsp.decorators.main_jsp._jspx_meth_gwin_005flefttree_005f0(main_jsp.java:383)
at org.apache.jsp.decorators.main_jsp._jspService(main_jsp.java:241)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:654)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:557)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:481)
at com.opensymphony.sitemesh.compatability.OldDecorator2NewDecorator.render(OldDecorator2NewDecorator.java:46)
at com.opensymphony.sitemesh.webapp.decorator.BaseWebAppDecorator.render(BaseWebAppDecorator.java:33)
at com.opensymphony.sitemesh.webapp.SiteMeshFilter.doFilter(SiteMeshFilter.java:84)
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请高手解决！