空指针的那个异常怎么解决？

Question

视屏里面校验的时候，那个空指针异常，如何消除？

java.lang.NullPointerException
    at java.util.ComparableTimSort.countRunAndMakeAscending(ComparableTimSort.java:316)
    at java.util.ComparableTimSort.sort(ComparableTimSort.java:184)
    at java.util.Arrays.sort(Arrays.java:1246)
    at com.utility.yongfeim.CheckUtil.checkSignature(CheckUtil.java:12)
    at com.myservlet.yongfeim.WeixinSerlet.doGet(WeixinSerlet.java:31)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:723)