Gracefully handle camera permissions denied

[AsturaPhoenix]

Right now if camera permissions are denied the compass throws an error and shows a spinner forever where the camera display would be. Instead, catch the exception and hide the spinner. If we have a setting in the app to enable/disable the camera, possibly disable it.

This might be a challenge to test, as the camera permissions happen natively. Our best bet might be to mock out the permission failure in a widget test.