Subtitles download fails for media imported from third party apps

When playing media imported from third party apps, it will be stored in /Documents/Inbox/ in the application context. When then downloading subtitles from OSO, it will be attempted to be stored in that folder, too, which silently fails. Then, loading of the subtitles fails as the file is not there when attempted to be read.

This is a major regression in 3.3 leading to a lot of screaming on the app store.