Incorrect behavior if torrent file is not readable

[van-de-bugger]

transmission-remote-gtk v1.6.0 on Linux (Fedora 38).

Steps to reproduce:

1. Get any torrent file, e. g. test.torrent.
2. Make it unreabable, e. g. chmod a-rwx test.torrent.
3. Start TRG.
4. Press Ctrl+O, TRG shows "Add a Torrent" dialog.
5. Navigate to the directory where test.torrent resides and add it.
6. Since the file is not readable, TRG shows error box "Failed to open file ".../test.torrent": open failed(): Permission denied". That's ok, it is expected behavior. Push "Ok" button.

Actual behavior:

TRG shows "Add Torrent" dialog with torrent file "test.torrent" and *empty list of files in the torrent".

Expected behavior:

Since TRG failed to read the torrent file, it has nothing to do (besides showing the error message). There is no point to let user choose priority and other download options, since these no torrents will be added anyway.

See also:

• Issue 221.
• PR 222.