[minor] Remove unnecessary exists check over singleton list
[minor] Remove unnecessary exists check over singleton list

Reviewed By: jvillard

Differential Revision: D25305166

fbshipit-source-id: 1bfebf752

facebook/infer,jvillard/infer,facebook/infer,facebook/infer,jvillard/infer,facebook/infer,jvillard/infer,facebook/infer,facebook/infer,jvillard/infer,jvillard/infer,jvillard/infer,jvillard/infer,facebook/infer