If you have a broken file, Nikola crashing is the correct behavior, because that file probably won’t be recognized by browsers either, and you will end up with garbage output. In my opinion, this can be left as-is for the user to fix themselves.
I see the value of what you're saying.
Bad images should not reach the browser. So isn't it better to log an error and not process the image further. This ensures that the image does not reach the output and also users won't have to see an ugly back-trace.
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.