Failed downloads are treated as complete

[typhoon71]

Bug description
Failed downloads are treated as complete and are not retried once restarted.

Steps to reproduce

• Have some monitor active
• launch grabber
• if the download fails, it's still counted as success (see last success colum on monitors)

Expected behavior
Failed download should not be counted as downloaded and retried next monitor tick.
Also the date should stay the previous one, it failed the synch after all.

Context

• yesterday was watching the log and saw that all downloads failed
• I noticed that the page would get parsed, the new pics recognized, but then they failed to download
• I realized that the source site (yandere) was down / in pieces / ...
• I noticed last success colum on monitors was updated with current date - even if they failed to download
• also today, with the site back up, those pics weren't resumed
• I had to force a full recheck (download all) to get them

System information

• OS: [e.g. Windows 7 SP1]
• Grabber version: [e.g. 7.11.2]