[quandary] ok to have no post if start node has no succs
[quandary] ok to have no post if start node has no succs

Reviewed By: sblackshear

Differential Revision: D3991275

fbshipit-source-id: 5f8c4be

jvillard/infer,facebook/infer,jvillard/infer,kageiit/infer,jsachs/infer,kageiit/infer,ropas/infer,blzq/infer,ryoon/infer,jsachs/infer,xennygrimmato/infer,jvillard/infer,ryoon/infer,ropas/infer,ryoon/infer,facebook/infer,facebook/infer,facebook/infer,blzq/infer,jsachs/infer,ropas/infer,kageiit/infer,ropas/infer,blzq/infer,jsachs/infer,xennygrimmato/infer,ryoon/infer,jvillard/infer,jvillard/infer,facebook/infer,jvillard/infer,blzq/infer,blzq/infer,blzq/infer,kageiit/infer,ryoon/infer,ropas/infer,kageiit/infer,xennygrimmato/infer,jsachs/infer,xennygrimmato/infer,kageiit/infer,facebook/infer,xennygrimmato/infer,xennygrimmato/infer,facebook/infer,xennygrimmato/infer,kageiit/infer,ropas/infer,ryoon/infer,jvillard/infer,jsachs/infer