Fix NPE in PackageManagerInternal.getPackagesForAppId().

The original code would cause NPE for ejected non-shared-user
packages, because List.of() requires the argument to be non-null and
throws an NPE otherwise.

In order to be consistent with the shared user case, we should return
empty list when the APK isn't available.

Bug: 263504888
Test: presubmit
Change-Id: Iefd80188a8dc6be5cd49b3b813aa809fd3489fff