recent versions of swift-corelibs-foundation don't crash here
recent versions of swift-corelibs-foundation don't crash here

- instead of insta-crashing, `cancel(byProducingResumeData:)` now
  just calls the completion handler with `nil`. Reasonable!

glessard/deferred,glessard/swiftian-dispatch,glessard/async-deferred,glessard/deferred