Don't let NotificationMediaManager cause NPEs

If setUpWithPresenter() hasn't been called on NotificationMediaManager,
it can NPE when serving up APIs.

Long term, we probably need a way to make sure classes which need to bet
set up don't do anything before they get that chance.

Test: open camera, kill sysui, make sure it boots
Change-Id: Idc41bf9aeecda2bcc55c03b4c027c15fbc880a4f
Fixes: 119322135

packages/SystemUI/src/com/android/systemui/statusbar/NotificationMediaManager.java

@@ -280,7 +280,10 @@ public class NotificationMediaManager implements Dumpable {
         if (metaDataChanged) {
             getEntryManager().updateNotifications();
         }
-        mPresenter.updateMediaMetaData(metaDataChanged, true);
+
+        if (mPresenter != null) {
+            mPresenter.updateMediaMetaData(metaDataChanged, true);
+        }
     }
 
     public void clearCurrentMediaNotification() {