Fix _newest_commit_hash not set on updating fresh source install

fixes mr-orange/Sick-Beard#578
Merge pull request #580 from itofzo/fix_issue_578_empty_newest_commit_hash_source_update_PIS

Fix _newest_commit_hash not set on updating fresh source install
Merge branch 'Pistachitos' of https://github.com/mr-orange/Sick-Beard into ThePirateBay