Summary:
Fixing T31692652.
I couldn't reproduce this on my local tests - (tried non-utf chars, deleted memory, onverted vectors that are erased).
My guess - an illegal string cannot be converted to NSSString and thus we return nil when the folly::dynamic type is STRING.
See task for additional details.
Reviewed By: nubbel
Differential Revision: D8952714
fbshipit-source-id: c87af523efca1b96a4cf3d5d26fa5c16ed5cd773
333ceac957