Invalid indexed media file

[AbsurdlySuspicious]

Reported in #525

Downloaded media creates a 0 byte ghost copy in /Internal Memory/Pictures/

the file itself doesn't appear to exist, though it shows up in all gallery apps I tested. The exact path is /storage/emulated/0/Pictures/.jpg.

Main suspect is:

https://github.com/Tunous/Dawn/blob/9e8d38757a5eadbd9fdce096777414bc69736564/app/src/main/java/me/saket/dank/notifs/MediaDownloadService.java#L632-L649

just scanFile should be enough, needs testing