fix deleting non-existing repo

lib/gitlab/backend/gitolite_config.rb

@@ -87,7 +87,9 @@ module Gitlab
     end
     def destroy_project(project)
-      FileUtils.rm_rf(project.repository.path_to_repo)
+      if project.repository
+        FileUtils.rm_rf(project.repository.path_to_repo)
+      end
       conf.rm_repo(project.path_with_namespace)
     end