Handle FromConfig in withFallback also, see #944

akka-actor-tests/src/test/scala/akka/routing/ConsistentHashingRouterSpec.scala

@@ -51,7 +51,7 @@ class ConsistentHashingRouterSpec extends AkkaSpec(ConsistentHashingRouterSpec.c
   import akka.routing.ConsistentHashingRouterSpec._
   implicit val ec = system.dispatcher
 
-  val router1 = system.actorOf(Props[Echo].withRouter(ConsistentHashingRouter()), "router1")
+  val router1 = system.actorOf(Props[Echo].withRouter(FromConfig()), "router1")
 
   "consistent hashing router" must {
     "create routees from configuration" in {

akka-actor/src/main/scala/akka/routing/ConsistentHashingRouter.scala

@@ -199,6 +199,7 @@ case class ConsistentHashingRouter(
    * that can't be defined in configuration.
    */
   override def withFallback(other: RouterConfig): RouterConfig = other match {
+    case fromConfig: FromConfig ⇒ this
     case otherRouter: ConsistentHashingRouter ⇒
       val useResizer =
         if (this.resizer.isEmpty && otherRouter.resizer.isDefined) otherRouter.resizer