fix:解决无考试时防止重名循环报错的问题

src/modules/teach-tool/examination-manager/AddExam.tsx

@@ -277,7 +277,7 @@ function AddExam(props: any) {
     // 校验考试名称是否存在
     function checkExist(examName: any) {
         var result:any = null;
-        examList.forEach((item:any) => {
+        examList.length > 0 && examList.forEach((item:any) => {
             if (result != null) {
                 return result;
             }