Fix remoting logging DefaultAddress race condition (#7305)

Author: Arkatufus

src/core/Akka.Remote/RemoteActorRefProvider.cs

@@ -189,7 +189,7 @@ public ActorPath RootPath
         public Deployer Deployer { get; protected set; }
 
         /// <inheritdoc/>
-        public Address DefaultAddress { get { return Transport.DefaultAddress; } }
+        public Address DefaultAddress { get { return Transport?.DefaultAddress; } }
 
         private Information _serializationInformationCache;
 

src/core/Akka/Event/Logging.cs

@@ -112,8 +112,15 @@ public static string FromActor(IActorContext actor, ActorSystem system)
 
         public static string FromActorRef(IActorRef a, ActorSystem system)
         {
-            var defaultAddress = system.AsInstanceOf<ExtendedActorSystem>().Provider.DefaultAddress;
-            return defaultAddress is null ? a.Path.ToString() : a.Path.ToStringWithAddress(defaultAddress);
+            try
+            {
+                var defaultAddress = system.AsInstanceOf<ExtendedActorSystem>().Provider.DefaultAddress;
+                return defaultAddress is null ? a.Path.ToString() : a.Path.ToStringWithAddress(defaultAddress);
+            }
+            catch // can fail if the ActorSystem (remoting) is not completely started yet
+            {
+                return a.Path.ToString();
+            }
         }
     }