Change MaxUnpool to accept tensors with 0-dim batch sizes. (#64082)
Summary:
Part of the fix for https://github.com/pytorch/pytorch/issues/38115.
Changes the `MaxUnpool` module to work with 0-dimensions batch sizes.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64082
Reviewed By: mrshenli
Differential Revision: D30793907
Pulled By: jbschlosser
fbshipit-source-id: d21aa665be5aa18f592b39ef7b4e3cbc632e21ed