fix fairseqlm decoder with flashlight chnages (#1617)
fix fairseqlm decoder with flashlight chnages (#1617)

Summary:
fixes fairseqlm integration with flashlight (formerly wav2letter) decoder

Pull Request resolved: https://github.com/fairinternal/fairseq-py/pull/1617

Reviewed By: xuqiantong

Differential Revision: D26415650

Pulled By: alexeib

fbshipit-source-id: 813684ba55047e92378f508101ff1eec55754420

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq