`isObjectEqual` will throw exception when object contains null value

[CzBiX]

Version

2.7.0

Reproduction link

https://jsfiddle.net/t8gpt9mk/

Steps to reproduce

Click router link in page.

What is expected?

Query in url changed.

What is actually happening?

Throw TypeError.

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This code works well on vue-router 2.5.3, and bug introduce by pull request #1425.

[posva]

Thanks for a more comprehensive bug report! 😄

[tebaly]

May be omit query parameter if is Null, like axios?