Version

3.0.2

Reproduction link

https://plnkr.co/edit/yJJpcKuhYQwdOk3nZcZs?p=preview

Steps to reproduce

1. Start with the url /?q=foo&color=bar.
2. this.$router.push({query: {q: 'foo', offset: undefined}})

What is expected?

I expect the url to change to /?q=foo

What is actually happening?

The url does not change

I'm doing search filtering using query params. Every time I change a filter, I
add/remove/modify the appropriate param, and reset my pagination by setting
an offset param to undefined. In my app, the combination of removing a param
and offset not being set to begin with, causes the route not to update.

This issue is easy enough to work around, but it took me a while to figure out
what was going on.