Ensure no empty vector before call to appendVector
Ensure no empty vector before call to appendVector

Reviewed By: ssj933

Differential Revision: D37087578

fbshipit-source-id: 5309819a72f70c216433613650e7b502e80b3c25

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