bucket: update changelog

Signed-off-by: Jacob Colvin <Jacob.Colvin@8451.com>

CHANGELOG.md

@@ -15,6 +15,7 @@ We use *breaking* word for marking changes that are not backward compatible (rel
 
 - [#2238](https://github.com/thanos-io/thanos/pull/2238) Ruler: Fixed Issue #2204 bug in alert queue signalling filled up queue and alerts were dropped
 - [#2231](https://github.com/thanos-io/thanos/pull/2231) Bucket Web - Sort chunks by thanos.downsample.resolution for better grouping
+- [#2271](https://github.com/thanos-io/thanos/pull/2271) Bucket Web: Fixed Issue #2260 bucket passes null when storage is empty
 
 ## [v0.11.0](https://github.com/thanos-io/thanos/releases/tag/v0.11.0) - 2020.03.02