Extension Pdf versus PDF

zanodor

I have recently found in my use case mentioned [here](https://forums.zotero.org/discussion/105861/data-syncing-issues-on-ios-since-updates-1-0-16-17#latest) that files with extensions PDF with capital letters were not found.
Upon renames to lowercase `pdf`, files were found after restarting iOS app.

No biggie, though

Cheers