Fix isAutoRevokeWhitelisted vulnerability

Apps should not be allowed to programatically check whether a given
package is installed on the current device.

But, currently, isAutoRevokeWhitelisted allows app to do so by invoking
isAutoRevokeWhitelisted for a package name, then checking for an error:

- if NullPointerException is thrown, the package does not exist, or
- if SecurityException is thrown, the package exists.

The NullPointerException occurs in PermissionManagerService on the line:

    final int packageUid = UserHandle.getUid(userId, pkg.getUid());
                                                      ^ null

The solution is to:

- avoid a NullPointerException by moving the above line of code down
  below where we've already null-checked 'pkg' (checkAutoRevokeAccess),
- return false when the target app doesn't exist, and
- return false when the calling app doesn't have permission to access
  the target app (via filterAppAccess).

Bug: 186404493
Test: manual
Change-Id: Ibae43d92b8eee24a0e56f08c878a7fe793833287

services/core/java/com/android/server/pm/permission/PermissionManagerService.java

@@ -1381,12 +1381,16 @@ public class PermissionManagerService extends IPermissionManager.Stub {
 
         final AndroidPackage pkg = mPackageManagerInt.getPackage(packageName);
         final int callingUid = Binder.getCallingUid();
-        final int packageUid = UserHandle.getUid(userId, pkg.getUid());
+        if (mPackageManagerInt.filterAppAccess(packageName, callingUid, userId)) {
+            return false;
+        }
 
         if (!checkAutoRevokeAccess(pkg, callingUid)) {
             return false;
         }
 
+        final int packageUid = UserHandle.getUid(userId, pkg.getUid());
+
         final long identity = Binder.clearCallingIdentity();
         try {
             return mAppOpsManager.checkOpNoThrow(