[quant][mobile] Return for conv with empty batch (#37779)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37779
We should just return empty output
Test Plan: Imported from OSS
Differential Revision: D21385789
fbshipit-source-id: 4b42f5aaebabfa3f329ed74356bddb33daad98d5
