Fixed Optional argument in Message Updated event

src/Discord.Net/WebSocket/DiscordSocketClient.cs

@@ -1262,7 +1262,10 @@ namespace Discord.WebSocket
                                                 after = channel.CreateMessage(author, data);
                                         }
                                         if (after != null)
-                                            await _messageUpdatedEvent.InvokeAsync(Optional.Create(before), after).ConfigureAwait(false);
+                                            if (before == null)
+                                                await _messageUpdatedEvent.InvokeAsync(Optional.Create<IMessage>(), after).ConfigureAwait(false);
+                                            else
+                                                await _messageUpdatedEvent.InvokeAsync(Optional.Create<IMessage>(before), after).ConfigureAwait(false);
                                     }
                                     else
                                     {