Skip previously downloaded files and photos

[Pablo2m]

I almost finished downloading messages from about 120 groups, my next step is to download the files and photos from them. Is it possible for the archiver to verify if the download does not exist before downloading it?

[ROCKETEER5215]

I just tested downloading photos from a group that doesn't have any and nothing was displayed in the console. In the archive.log it shows that the album API returns None two times then just stops at line 275 since the list is empty. We need to check if albums is empty and if it is then have a logger.error("This group doesn't have any photos to download")

[ROCKETEER5215]

Currently it doesn't do anything like that I think it could do it, but it would take a lot of work to make it happen.