Fix NullPointerException of LocalMediaManager

Bug: LocalMediaManager
Test: build pass

Change-Id: Ib53cb11d28669486573777be992711200a39cd85

src/com/android/settings/media/MediaOutputIndicatorWorker.java

@@ -157,7 +157,11 @@ public class MediaOutputIndicatorWorker extends SliceBackgroundWorker implements
         return mMediaDevices;
     }
 
+    @Nullable
     public MediaDevice getCurrentConnectedMediaDevice() {
+        if (mLocalMediaManager == null) {
+            return null;
+        }
         return mLocalMediaManager.getCurrentConnectedDevice();
     }