DO NOT MERGE Protect against NPE in FusionEngine.java.

Cherry-pick of Ic49a069eef47a62fb1e0c6f284a705a62c6ae232

Bug: 7629406
Change-Id: Ia04dba9496b02755678b43e12834e992f63ee45b

packages/FusedLocation/src/com/android/location/fused/FusionEngine.java

@@ -249,7 +249,11 @@ public class FusionEngine implements LocationListener {
             }
         }
 
-        mCallback.reportLocation(mFusedLocation);
+        if (mCallback != null) {
+          mCallback.reportLocation(mFusedLocation);
+        } else {
+          Log.w(TAG, "Location updates received while fusion engine not started");
+        }
     }
 
     /** Called on mLooper thread */