Allow accessing missing-buckets-header in CORS requests (#3270)

* allow accessing missing-buckets-header in cors requests (fixes #3269)

* update changelog

* fix syntax error

CHANGELOG.md

@@ -19,7 +19,7 @@ For upgrade instructions, please check the [migration guide](MIGRATIONS.md).
 
 ### Fixed
 
-- 
+- Fixed a bug which caused data to not be displayed correctly if adjacent data does not exist.[#3270](https://github.com/scalableminds/webknossos/pull/3270)
 
 ### Removed
 

webknossos-datastore/app/DsRequestHandler.scala

@@ -14,7 +14,8 @@ class DsRequestHandler @Inject() (router: Router, errorHandler: HttpErrorHandler
           "Access-Control-Allow-Origin" -> "*",
           "Access-Control-Max-Age" -> "600",
           "Access-Control-Allow-Methods" -> "POST, GET, DELETE, PUT, HEAD, PATCH, OPTIONS",
-          "Access-Control-Allow-Headers" -> request.headers.get("Access-Control-Request-Headers").getOrElse(""))
+          "Access-Control-Allow-Headers" -> request.headers.get("Access-Control-Request-Headers").getOrElse(""),
+          "Access-Control-Expose-Headers" -> "MISSING-BUCKETS")
       })
     } else {
       super.routeRequest(request)