Error occurs in sentinel-dashboard frontend

[lonecloud]

Issue Description

前端页面出现报错信息

Describe what happened (or what feature you want)

按照正常启动Application后，访问localhost:8080.直接进入到页面中，点击搜索后，出现一个无标题选项，点击展开后报错

Describe what you expected to happen

如果无应用，则直接不显示就好了。

How to reproduce it (as minimally and precisely as possible)

1. 不运行任何关联sentinel应用
2. 直接启动dashboard
3. 进入到页面
4. 点击搜索
5. 点击左侧菜单空白框，出现菜单
6. 点击子菜单，无反应，控制台报错

Tell us your environment

windows7

Anything else we need to know?

[sczyh30]

Thanks for reporting! Would you like to fix this and send a PR to contribute?