Get.defaultDialog custom property never used in code.

[anees4ever]

Describe the bug
Get.defaultDialog property 'custom' is never used in the code. So passing the argument does not deliver the expected output.

**Reproduction code
import 'package:get/get.dart';

Get.defaultDialog(
title: 'Loading the data...',
custom: const SizedBox(
height: 100,
width: 100,
child: Center(child: CircularProgressIndicator()),
),
barrierDismissible: false,
);

To Reproduce
Steps to reproduce the behavior:

1. Run the above code
2. See error: We expect the loading spinner to show on the dialog, but it will not display that. Only the title will be visible

Expected behavior
A dialog with title 'Loading the data....' and a rotating spinner.

Getx Version:
4.6.6

[anees4ever]

If allowed, I can raise a pull request with a possible fix. I did it for my local project.