prevent exception in rescue block in rare cases

 prevent exception in rescue block in rare cases when update_last_fetch failed

Background:
- I have a rss feed that has published dates of 
     <pubDate>Mon, 01 Jan 0001 00:00:00 +0100</pubDate>
- An error occurs while processing the content of the feed.
- FeedRepository.update_last_fetched tries to set the date -> this failes on heroku because of timestamp corrections to year 0000
- in the rescue block then the status will be set and saved, but with still the last_updated timestamp set on the @feed
- a @feed.reload fixes this behaviour and the whole task 'rake fetch_feeds' runs through