fix(接口测试): 修复场景清空断言的缺陷

--bug=1027300 --user=王孝刚 【接口测试】场景引用case和场景的原始断言-点击清空JSONPath断言-断言被删除了
https://www.tapd.cn/55049933/s/1384927

api-test/frontend/src/business/definition/components/assertion/ApiAssertions.vue

@@ -247,7 +247,12 @@ export default {
       this.assertions.jsonPath.push(jsonItem);
     },
     clearJson() {
-      this.assertions.jsonPath = [];
+      if (this.assertions.jsonPath) {
+        const tmpArr = this.assertions.jsonPath.filter((item) =>
+          !item.label
+        );
+        this.assertions.jsonPath = tmpArr;
+      }
     },
   },
 };