ctx.query is not a plain object while ctx.params and ctx.request.body is
![image](https://user-images.githubusercontent.com/8615787/84727329-5c481c00-afc1-11ea-8adf-918ddf11792c.png)

As screenshot shows that ctx.query has no method `hasOwnProperty` from prototype

Which causes some package depends on `ctx.query.hasOwnProperty` calling an undefined method.


I am using koa@2.11.0