fix add_histogram_raw (#20688)
Summary:
This is a porting of the fix from:
https://github.com/lanpa/tensorboardX/issues/421
cc orionr
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20688
Reviewed By: NarineK
Differential Revision: D15415093
Pulled By: orionr
fbshipit-source-id: d32a6298218fbc6fe315aa0f18b57e0c8ef92627
