Revert D30038175: Improve IMethod::getArgumentNames to deal with empty argument names list
Test Plan: revert-hammer
Differential Revision:
D30038175 (https://github.com/pytorch/pytorch/commit/64b3ab64078c2400656544a8f4e6ccfc56009a89)
Original commit changeset: 46f08dda9418
fbshipit-source-id: 604735d2300487a0b75890b330d7ba5b3e7145b2
