Summary:
This fixes an issue in the C++ TurboModule codegen where optional return types would result in a compiler error because they were not being defaulted to `null` when converting to `jsi::Value`.
Changelog:
Internal
Reviewed By: javache
Differential Revision: D36989312
fbshipit-source-id: 525f9ce7a5638ba5a655fa69ba9647978030ab0b