Fix prefetching in range mode with args

[lukasbesch]

Prefetching in range mode with args() has the issue that opts.page is NaN on the prefetched call of the fetchPage() function.
I wrote a failing test and a fix, but the test does not succeed yet.
The example seems to be working though.

For the test:
I think another call of nextTick() is necessary (before changing pageTo) to allow the second promise to resolve.
But that alone does not work yet.

[MaxGfeller]

Thanks for the pull request - and sorry for the delay! I added a few await nextTick() where it's neccessary, but there seems to be a different error now. Could you look into that @lukasbesch?