Pull Request for Issue #29565.

Summary of Changes

Some of our List base custom fields like SQL uses OptionsRule https://github.com/joomla/joomla-cms/blob/4.2-dev/libraries/src/Form/Rule/OptionsRule.php to validate it's data. This rule requires a valid $form object to validate data in case the options for the field not defined in XML but dynamic defined (for example, from database) via getOptions method of the field type

This PR changes logic of checkDefaultValue method in FieldModel class to handle default value properly for these kind of custom fields. It is a bug fix, but I decided to implement the change to 4.3 branch so that we have more time for reviewing and testing the change. I also includes the change from PR #39354 (for 4.2 branch) so to avoid merge conflict.

Ping @laoneo for checking this change.

Testing Instructions

1. Use Joomla 4.3
2. Follow instructions at #29565 , confirm the issue
3. Apply patch, confirm the issue fixed.

Link to documentations

Please select:

• Documentation link for docs.joomla.org:

• No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed