if router query have null or undefined value, will throw error

[svkd9]

Version

2.7.0

Reproduction link

https://github.com/vuejs/vue-router/blob/v2.7.0/src/util/route.js#L86

Steps to reproduce

const routerQuery = {
a: null,
b: undefined
}
this.$router.push({name: 'routerName', query: routerQuery})

What is expected?

no error

What is actually happening?

throw error 'Cannot convert undefined or null to object'

---

i think the problem maybe in https://github.com/vuejs/vue-router/blob/v2.7.0/src/util/route.js#L86

typeof aVal === 'object' ====> Object.prototype.toString.call(aVal) === '[object Object]'

[posva]

Dup of some other issue, PR to fix this at #1568