Fix NullPointerException at VolumeSliceHelper

Race condition happens on accessing a map while system is destroying it.

Test: manual, robotest
Fixes: 188114877
Change-Id: I245121b95d1d4db02e3107a47c6d3ae13a5d32e5

src/com/android/settings/slices/VolumeSliceHelper.java

@@ -111,6 +111,7 @@ public class VolumeSliceHelper {
 
     private static void handleStreamChanged(Context context, Intent intent) {
         final int inputType = intent.getIntExtra(AudioManager.EXTRA_VOLUME_STREAM_TYPE, -1);
+        synchronized (sRegisteredUri) {
             for (Map.Entry<Uri, Integer> entry : sRegisteredUri.entrySet()) {
                 if (entry.getValue() == inputType) {
                     context.getContentResolver().notifyChange(entry.getKey(), null /* observer */);
@@ -118,10 +119,13 @@ public class VolumeSliceHelper {
                 }
             }
         }
+    }
 
     private static void notifyAllStreamsChanged(Context context) {
+        synchronized (sRegisteredUri) {
             sRegisteredUri.forEach((uri, audioStream) -> {
                 context.getContentResolver().notifyChange(uri, null /* observer */);
             });
         }
     }
+}