IllegalStateException when importing config data

[Centaur]

java.lang.IllegalStateException: UT000002: The response has already been started
at io.undertow.server.HttpServerExchange.setStatusCode(HttpServerExchange.java:1353)
at com.gtan.repox.admin.WebConfigHandler$.respondEmptyOK(WebConfigHandler.scala:70)
at com.gtan.repox.admin.WebConfigHandler$$anonfun$setConfigAndRespond$1.apply(WebConfigHandl
er.scala:46)
at com.gtan.repox.admin.WebConfigHandler$$anonfun$setConfigAndRespond$1.apply(WebConfigHandl
er.scala:44)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
at scala.concurrent.impl.ExecutionContextImpl$AdaptedForkJoinTask.exec(ExecutionContextImpl.
scala:121)
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.pollAndExecAll(ForkJoinPool.java:1253)
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1346)
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
03-11 23:44:52.795 DEBUG c.gtan.repox.config.ConfigPersister akka://repox/user/ConfigPersister