Allow version 1.3.1 to work in strict mode

[timcurzon]

Hi guys - I work with @far-blue at Namesco. We are currently using the old-ish 1.3.1 version of NestedTypes and recently needed to get said version to run in strict mode. So, here's a PR that covers the changes to do that. Note that tests that previously passed still pass (no new fails).

Whether you want to do anything with this PR I'm not sure, given the age of the codebase 😄

[gaperton]

Hi. I think I gonna merge this PR and release the update for 1.3. Thanks for the fixes.

[far-blue]

Hi :)

any movement on this?