Only reply to an invalid command if it came from a private chat

main.go

@@ -92,7 +92,9 @@ func handleMsg(ctx context.Context, entities tg.Entities, u *tg.UpdateNewMessage
 			return nil
 		default:
 			fmt.Println("  (invalid cmd)")
+			if fromGroup != nil {
 				_, _ = telegramSender.Reply(entities, u).Text(ctx, errorStr+": invalid command")
+			}
 			return nil
 		}
 	}