bug: not tolerating archives with bad/missing meta data, but which are extractable

[rwperrott]

In Linux common desktop archive tools can open these defective archives, e.g. XArchiver. It can be stupid stuff like a missing end-of-file directory in zip (cbz) files, or a missing end of file marker. It's annoying having to handle these file by extracting, then recompressing, so that the can be reprocessed. I suspect that switching to 7z libraries for archives could fix this.