Added getInitialUserInfo() to ICar.aidl.

Test: atest CarServicesTest:com.android.internal.car.CarHelperServiceTest \
            CarServiceUnitTest:com.android.car.user.CarUserServiceTest
Test: m -j libcarpowermanager

Bug: 150222501
Bug: 146207078
Bug: 150399261

Change-Id: I78556aa72f677db809732cbc2b7cc9c6da361794
diff --git a/service/src/com/android/car/user/CarUserService.java b/service/src/com/android/car/user/CarUserService.java
index 706f6e5..ed9a59c 100644
--- a/service/src/com/android/car/user/CarUserService.java
+++ b/service/src/com/android/car/user/CarUserService.java
@@ -480,6 +480,7 @@
     @Override
     public void getInitialUserInfo(int requestType, int timeoutMs,
             @NonNull IResultReceiver receiver) {
+        Objects.requireNonNull(receiver, "receiver cannot be null");
         UsersInfo usersInfo = getUsersInfo();
         mHal.getInitialUserInfo(requestType, timeoutMs, usersInfo, (status, resp) -> {
             try {