small implementation error in torchattacks.DeepFool

[LaurenzBeck]

I currently use DeepFool as an estimate for the distance to the decision boundary of a classifier, as suggested in the paper: https://arxiv.org/abs/2002.01810v1

I used the implementation from torchattacks because I found the implementation from the LTS4/DeepFool repo hard to understand and work without throwing errors. In the implementation from torchattacks I found an implementation error, that returned the original images as perturbation when the classifier already misclassified the image. Harry24k/adversarial-attacks-pytorch#51

This might also be the case in this repo, but I havent checked, just wanted to let you know.