fix(接口测试): 修复接口编辑页删除唯一case修改api参数点击保存仍弹出一键同步弹框问题

--bug=1028170 --user=郭雨琦
https://www.tapd.cn/55049933/bugtrace/bugs/view/1155049933001028170

api-test/frontend/src/business/definition/components/complete/EditCompleteHTTPApi.vue

@@ -1138,6 +1138,8 @@ export default {
       apiTestCaseCount({ id: this.httpForm.id }).then((response) => {
         if (response.data > 0) {
           this.httpForm.caseTotal = response.data;
+        } else {
+          this.httpForm.caseTotal = 0;
         }
       });
     },