求助一下为什么有时候创建表单之后会报错

幕僚的七

有时候就不会报错

[2017-10-31 18:16:38] [ERROR] [org.jeecgframework.core.common.exception.GlobalExceptionResolver:86] 全局处理异常捕获:
java.lang.NullPointerException
        at org.jeecgframework.web.cgform.controller.config.CgFormHeadController.delField(CgFormHeadController.java:220)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:747)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:676)
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
        at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:863)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.jeecgframework.core.aop.GZipFilter.doFilter(GZipFilter.java:119)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at com.alibaba.druid.support.http.WebStatFilter.doFilter(WebStatFilter.java:140)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
       .........