Merge pull request #313 from travis-ci/fix_sentry_errors

fix another sentry error

lib/travis/features.rb

@@ -111,6 +111,7 @@ module Travis
     #
     # By default, this return false.
     def owner_active?(feature, owner)
+      return false unless owner
       redis.sismember(owner_key(feature, owner), owner.id)
     end