fix potential heap-use-after-free in RequestsRegistry initialization.
fix potential heap-use-after-free in RequestsRegistry initialization.

Reviewed By: zhxchen17

Differential Revision: D20292852

fbshipit-source-id: bd74257d5759f045f96153c0578100a90c4b6976

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift