fix: 修复消息通知查询不到用户报错

--bug=1008980 --user=刘瑞斌 【站内信】提示报错 https://www.tapd.cn/55049933/s/1084951

frontend/src/business/components/notice/Notification.vue

@@ -165,7 +165,7 @@ export default {
           if (now - d.createTime > 10 * 1000) {
             return;
           }
-          d.user = this.userMap[d.operator];
+          d.user = this.userMap[d.operator] || {name: 'MS'};
           let message = d.user.name + getOperation(d.operation) + getResource(d) + ": " + d.resourceName;
           let title = d.type === 'MENTIONED_ME' ? this.$t('commons.mentioned_me_notice') : this.$t('commons.system_notice');
           setTimeout(() => {