Fixes PM.grantImplicitAccess for multi-user

This change fixes the security check in grantImplicitAccess to support
the case that the system user does not have an installed contacts
provider.

Fixes: 169684344
Test: atest android.provider.cts.contacts.ContactsContract_DirectoryTest
Change-Id: I2c80513a5dffa7ad92963e376ea85217f127f39a