Frameworks: privacy guard fix possible NPE

If the user flash a data app over recovery
(like a lot themed apps or gapps packages are doing)
the user will get into a bootloop because of an NPE
due an unknown state of the assigned userid

To fix it go same way like in PackageManagerService
Check if installUser exists if yes use
installUser.getIdentifier() to get the identifier
to call the provider settings value for the current
user.

Change-Id: Ie5f94a0d0a11ae24fdfdc8372c0433b26793b66e