GraphQLResponse.getRequestDetails should return nullable

[Emily]

It can return null, so ought to have ? so that folks using this from Kotlin don't end up with NPEs unexpectedly.

[paulbakker]

While you're correct that it should be nullable, this is a painful change to make. It will effectively fail compilation for every Kotlin app using this API. Simple fix, but quite annoying, specially for a non-major release.

[Emily]

@paulbakker true, though we've had at least one internal use get bitten by this. I think the minor annoyance of having to either add !! in a bunch of places, or actually properly null check is worth it.