Fix multinomial when input has 0 prob (#47386)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47386
Fix multinomail when input has 0 prob
Test Plan: buck test mode/dev-nosan //caffe2/test:torch -- "multinomial"
Reviewed By: ngimel
Differential Revision: D24699691
fbshipit-source-id: d88bb5be8cfed9da2ce6f6a8abd18e834fbde580
