How to reproduce the bug:
- Create a new XCode iOS project(project doesn't contain LaunchScreen file)
- Add new file using the LaunchScreen template
- Open TARGETS, select YourAppName, go to General, scroll down to App Icons and Launch Screen
- Try to setup Launch Screen File by pressing blue drop down button, select your "LaunchScreen"
- Switch from the General tab to another tab or file, then return to General
- Launch Screen file textfield is empty

SOLUTION: Don't use blue dropdown button(autofill), manually type 'LaunchScreen.storyboard'