[attribute form] Fix addition of features from a child feature dialog being added

[nirvn]

Description

This PR fixes #57474 . The regression was caused by this commit (5ac470c) merged back in July 2023.

@troopa81 , @Djedouas , I couldn't find an issue tied to the commit pushed back then, is it safe to revert? The change would need to be reviewed in any case as it triggers the above-mentioned regression whereas making the child feature attribute form modal prevents that form from creating other features (e.g. from an [+] add new feature button within the referenced relation editor widget).

[github-actions]

🪟 Windows builds ready!

Windows builds of this PR are available for testing here. Debug symbols for this build are available here.

(Built from commit 717506d)

[Djedouas]

Hi,

I couldn't find an issue tied to the commit pushed back then

The issue is described in the related PR #53562

It is not safe to revert, because this original issue would occur again.

#57474

Thanks for raising this new issue and showing the problem.

There is a UI/UX issue to fix here with code logic to modify...

[nirvn]

@Djedouas , I suspect though that the original fix will have to be rewritten away from making the child dialog blocking. It otherwise just block access to the main window unconditionally.

[nyalldawson]

I'd say in a choice between an issue which shows when adding features vs one which shows when using multi-edit, an issue in adding features is far more critical and should take precedence.

I think we should merge this and backport, and then find an alternative fix for the original issue.

[Djedouas]

@Djedouas , I suspect though that the original fix will have to be rewritten away from making the child dialog blocking. It otherwise just block access to the main window unconditionally.

All right 👍🏼

[nirvn]

@Djedouas , thanks for your understanding.