made update repoinfo script more failsafe when dealing with database entries not synced with filesystem

rhodecode/lib/update_repoinfo.py

@@ -73,7 +73,8 b' class UpdateCommand(BasePasterCommand):'
         else:
             repo_list = Repository.getAll()
         for repo in repo_list:
-            last_change = repo.scm_instance.last_change
+            last_change = (repo.scm_instance.last_change if repo.scm_instance
+                           else datetime.datetime.utcfromtimestamp(0))
             repo.update_last_change(last_change)
 
     def update_parser(self):