check pruned attributes before deleting (#41913)
Summary:
I copyed a pruned model after deleteing the derived tensors. In order to be able to reparameter the model, we should check the existence of the tensors here.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/41913
Reviewed By: izdeby
Differential Revision: D22703248
Pulled By: mrshenli
fbshipit-source-id: f5274d2c634a4c9a038100d8a6e837f132eabd34
