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

services/core/java/com/android/server/pm/ComputerEngine.java

@@ -5624,7 +5624,12 @@ public class ComputerEngine implements Computer {
             return sus.getPackages();
         } else if (settingBase instanceof PackageSetting) {
             final PackageSetting ps = (PackageSetting) settingBase;
-            return List.of(ps.getPkg());
+            final AndroidPackage pkg = ps.getPkg();
+            if (pkg != null) {
+                return Collections.singletonList(pkg);
+            } else {
+                return Collections.emptyList();
+            }
         } else {
             return Collections.emptyList();
         }