Map ObsListDialog index from proxy model back to the source

[moble]

Description

I contributed #4098, but failed to notice that after sorting, when you double-click on a row, it segfaults.

This PR fixes the segfault. The problem was that the double‐click slot is using an index from a proxy model without mapping it back to the source (itemModel). When you sort the tree view, you set a new proxy model on the view. Then the QModelIndex passed to selectAndGoToObject belongs to the proxy and must be mapped back to the source model before calling itemModel->itemFromIndex().

Screenshots (if appropriate):

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• This change requires a documentation update
• Housekeeping

How Has This Been Tested?

I've built the code, run it, and tested on my own observing list — including double-clicking on a row.

Test Configuration:

• Operating system: macOS 14.6.1
• Graphics Card: Apple M2 Max (Metal 3)

Checklist:

• My code follows the code style of this project.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (header file)
• I have updated the respective chapter in the Stellarium User Guide
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[github-actions]

Great PR! Please pay attention to the following items before merging:

Files matching src/**/*.cpp:

• Are possibly unused includes removed?

This is an automatically generated QA checklist based on modified files.

[alex-w]

Thanks for fix!