Merge pull request #567 from SickRage/cur-hash

Fix issue when restoring backup from another fork and the current com…

sickbeard/versionChecker.py

@@ -759,9 +759,14 @@ class SourceUpdateManager(UpdateManager):
 
         # try to get newest commit hash and commits behind directly by comparing branch and current commit
         if self._cur_commit_hash:
+            try:
                 branch_compared = sickbeard.gh.compare(base=self.branch, head=self._cur_commit_hash)
                 self._newest_commit_hash = branch_compared.base_commit.sha
                 self._num_commits_behind = branch_compared.behind_by
+            except Exception:  # UnknownObjectException
+                self._newest_commit_hash = ""
+                self._num_commits_behind = 0
+                self._cur_commit_hash = ""
 
         # fall back and iterate over last 100 (items per page in gh_api) commits
         if not self._newest_commit_hash: