Fix concurrent when tests from crashing
Fix concurrent when tests from crashing

One of the tests was crashing later due to pending promises continuing to resolve and somehow the array of values contained a `nil`. I rewrote the specific when to not depend on optionals.
allen-zeng/PromiseKit,mxcl/PromiseKit,mxcl/PromiseKit,allen-zeng/PromiseKit,mxcl/PromiseKit