[infer][backend] Only call the prover to check that an expression being dereferenced is not null after checking if the expression is associated with @Nullable
[infer][backend] Only call the prover to check that an expression being dereferenced is not null after checking if the expression is associated with @Nullable

Summary: I tested on Fresco and this reduced the number of calls to Prover.check_disequal by 30%.

Reviewed By: cristianoc

Differential Revision: D5237774

fbshipit-source-id: 377545e

facebook/infer,facebook/infer,blzq/infer,blzq/infer,ropas/infer,facebook/infer,blzq/infer,jvillard/infer,jvillard/infer,jvillard/infer,facebook/infer,facebook/infer,jvillard/infer,ropas/infer,ropas/infer,facebook/infer,blzq/infer,jvillard/infer,ropas/infer,blzq/infer,ropas/infer,blzq/infer,jvillard/infer,ropas/infer,facebook/infer,jvillard/infer