=act,rem #13946 fix handling of null parameters in Props

+ Props creation with nulls does not fail any longer
+ null values are now serialised properly and can be used in remote
  deployments too
+ added tests for Reflect.findConstructor
> does not change wire protocol, so that's open for discussion (if we
> want it to be more like SerialisedMessage or not)

Resolves #13946

akka-remote/src/test/scala/akka/remote/serialization/DaemonMsgCreateSerializerSpec.scala

@@ -16,9 +16,11 @@ import scala.concurrent.duration._
 
 object DaemonMsgCreateSerializerSpec {
   class MyActor extends Actor {
-    def receive = {
-      case _ ⇒
-    }
+    def receive = Actor.emptyBehavior
+  }
+
+  class MyActorWithParam(ignore: String) extends Actor {
+    def receive = Actor.emptyBehavior
   }
 }
 
@@ -45,6 +47,16 @@ class DaemonMsgCreateSerializerSpec extends AkkaSpec {
       }
     }
 
+    "serialize and de-serialize DaemonMsgCreate with FromClassCreator, with null parameters for Props" in {
+      verifySerialization {
+        DaemonMsgCreate(
+          props = Props(classOf[MyActorWithParam], null),
+          deploy = Deploy(),
+          path = "foo",
+          supervisor = supervisor)
+      }
+    }
+
     "serialize and de-serialize DaemonMsgCreate with function creator" in {
       verifySerialization {
         DaemonMsgCreate(