fix some bug

[zimo0o0omiz]

// if config.root not '/',skip it others may double,fix the problem,hope accept for example, url: http://zimolove3.gitee.io/blog/ root: /blog in your project,this may generate url like this "/blog/blog/about/index/1565320816536.png",it's wrong.the right should like this "/blog/about/index/1565320816536.png",so I change your code to fix this bug,hope you accept