discard unusable images

[sidphbot]

discard unusable images using a try..catch and subsequent length checking

[pabloppp]

To me, it would maybe make more sense to make sure that your dataset has no broken images before running any training on it, instead of silently failing on those images.
I feel like this PR adds a fix to a problem unrelated with alias-free gan, and only related to a specific dataset that should probably be fixed instead, idk 🤷

[rosinality]

I think it will be better to specify exceptions if exception handling is needed.

[sidphbot]

apologies, I agree it is not related to alias-free-gan. I was just trying to make it easier to run in collab environments while I am doing that myself. it is an awesome repo ! kudos!
feel free to reject the pull request, will specify the exceptions today.

[vsemecky]

As a software developer with 25 years of experience, here's how I see it: If we know about a potential error that may occur, we should treat it. And using try/catch is the obvious choice. So I agree with @sidphbot.