fix devirtualizer crash on native method
fix devirtualizer crash on native method

Summary:
fixes
`MethodDevirtualizer.cpp:151: assertion '!is_static(method) && code != nullptr' failed.`

Reviewed By: int3

Differential Revision: D5991555

fbshipit-source-id: a50c974498082c727b9ad099770dbb173858797b

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex