Binary UUID fetching may not return nil, otherwise could lead to a crash. Return an empty string instead
Exclude UUID fetching from simulator builds (workaround to get unit test targets build without problems)

- This now requires the testing of this feature to be done on an actual device, since it returns always empty strings on the simulator
- Once there is a better solution to get unit test targets build without problems this should be changed again, so testing of this feature is also possible using the simulator