Don't init user 0 in media service

Fixes: 144746966
Test: Manual
Change-Id: I67d9edb76efb3c8a336dd8757d7c3f8646fd4a19
(cherry picked from commit 72eb6734ea27acb7aee380ecbba309f445baa09f)
diff --git a/service/src/com/android/car/CarMediaService.java b/service/src/com/android/car/CarMediaService.java
index a2f5567..665643a 100644
--- a/service/src/com/android/car/CarMediaService.java
+++ b/service/src/com/android/car/CarMediaService.java
@@ -191,6 +191,9 @@
     }
 
     private void maybeInitUser() {
+        if (mCurrentUser == 0) {
+            return;
+        }
         if (mUserManager.isUserUnlocked(mCurrentUser)) {
             initUser();
         } else {