Even I have InfoPlist.xcstring string catalog file, I got a similar warning when I use "" value inside project.pbxproj file like:
INFOPLIST_KEY_NSLocationWhenInUseUsageDescription = "";
The warning was: ITMS-90738: Invalid purpose string value - The “” value for the NSLocationAlwaysAndWhenInUseUsageDescription key isn’t allowed in ...
I have to write full sentence inside project file even it is discarded during runtime.