Localization: "Add Locales" completes silently without creating any asset when only already-added locales are counted as selected

Steps to reproduce:

1. Create a new project
2. Install the Localization package (com.unity.localization)
3. Open Edit > Project Settings > Localization, click "Create", and add the English locale via "Add Locale" so one row will be greyed out on the next open
4. Click "Add Locale" and search for English, so only a few rows are listed, including the greyed one
5. Click "Select All"
6. Untick every row that is not greyed out, leaving no selectable locale ticked
7. Click "Add Locales" and choose any folder inside the project

Actual results: Add Locales" is still enabled although no selectable row is ticked. Clicking it opens the save-folder dialog, and after a folder is chosen, no Locale asset is created, nothing is logged, and the window closes as though the operation had succeeded

Expected results: No asset is created, so the window reports that nothing was added - or "Add Locales" is disabled because no selectable locale is ticked. The window must not close as if it had succeeded

Reproducible with versions: 1.5.12 (6000.5.7f1, 6000.6.0f1, 6000.7.0a6)

Tested on (OS): MacBook Pro - Tahoe 26.6.2

Notes:

• "Select All" does not tick the greyed-out, already-added rows, but they are still counted toward the selection total, which seems keeps the button enabled.