fix conditional in mean workaround (#16686)
Summary:
When trying to get a test to pass I was missing an exclamation mark. Instead now I just use a different function in the conditional
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16686
Differential Revision: D13935182
Pulled By: jamesr66a
fbshipit-source-id: 7525a1a829276641dbafe06734f03f6202df6b22
