URIError: URI malformed

### Vue.js & vue-router.js version

1.0.16, 0.7.11
### Steps to reproduce

由百度跳转过来的链接，里面带有如下的query

```
utm_term=%BC%CE%C0%EF%D6%D0%D0%C4%D7%E2%C1%DE
```

导致vue-router的代码执行到 `let url = decodeURI(location.pathname + location.search)`时会报错

```
Uncaught URIError: URI malformed
```
### What is Expected?

正常执行下去
### What is actually happening?

是否在处理`decodeURI`时可以有try catch之类的处理，不要因为这里出错就整个挂掉？
