Reproduction Steps:
1. Open User's project
2. Note user tests on Simulator. To test on device set Target SDK in Player Settings from "Simulator SDK" to "Device SDK"
3. Build to iOS
4. Deploy to device or simulator
5. Go to Home Screen (CMD+Shift+H in simulator)
6. Open Safari
7. Type "uritest://test"
8. In the popup that appears, click "Open"
9. Notice that Xcode breaks on line:

UIApplicationMain(argc, argv, nil, [NSString stringWithUTF8String:AppControllerClassName]);

10. Notice Xcode outputs:

libc++abi.dylib: terminating with uncaught exception of type NSException

Expected behaviour: Project opens on iOS device without any problem.
Actual result: Opening app from URI fails.

Reproduced on versions: Unity 5.5.0p1, 5.6.0b1
Could not reproduce on Unity 5.4.3p3 (crashes while building), 5.3.7p2 (freezes while building)