small fix for generating successive frame

[salco]

I had an looking like this post: https://stackoverflow.com/questions/58468944/image-object-has-no-attribute-read
So I change the notebook to allow the first frame to open differently. It's mostly a dirty trick in my opinion but it do the work for a demo project.
I'm open to change it if you need

[salco]

I think Image.open(current_image_path) should be done before the for to be cleaner.