Building a project for iOS with 'Launch Screen' set to 'Custom Storyboard' fails if only iPhone storyboard was setup

Steps to reproduce:

1. Open attached project (storyboard-bug.zip)
2. Switch to iOS
3. Check Player Settings/Splash Screen window
4. Notice that Launch Screen is set to Custom Storyboard for iPhone, but left as Default for iPad
5. Try to build the project

Actual results: Build fails wit "System.UnauthorizedAccessException: Access to the path '/path_to_project/storyboard-bug' is denied."

Expected results: Build succeeds and has correct launch screens set up for both iPhone and iPad.

Notes: If both iPhone and iPad storyboards are set up as "Custom Storyboard", then build succeeds.

Reproducible with versions: 2022.3.11f1, 6000.0.11f1

Not reproducible with versions: 2021.3.39f1