Fallback to original profile image from media.nostr.band

[brugeman]

If media.nostr.band returns 404 we should fallback to downloading the original profile image.

Here is roughly how I do it at nostr.band:

<img src='${media_url}' onerror="javascript:replaceImgSrc(this, ${orig_url})">
Not sure how to do that properly in react.