next(undefined) in navigation guard throws a TS error

[Thomasan1999]

Version

4.0.10

Reproduction link

https://codesandbox.io/s/vue-router-nextundefined-example-xz4yo

Steps to reproduce

1. Use a navigation guard.
2. Write next(undefined)

What is expected?

next(undefined) works the same way as next() since empty argument is treated as undefined in JS.

What is actually happening?

next(undefined) throws
Argument of type 'undefined' is not assignable to parameter of type 'NavigationGuardNextCallback'

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It seems that the NavigationGuardNext interface must be changed to either have an undefined argument as a separate row or to make one of the options optional.