fix(接口测试): 场景脚本兼容旧数据无断言

(cherry picked from commit 00f4cf449c)

frontend/src/views/api-test/scenario/components/common/scriptOperationDrawer.vue

@@ -170,6 +170,7 @@
                 ...props.detail,
                 processorType: RequestConditionProcessor.SCRIPT,
                 polymorphicName: 'MsScriptElement',
+                children: props.detail.children || defaultScript.children,
               }
             : defaultScript
         );