SystemUI: Fix data activity overlay not being removed when data is disabled

If mobile data connection is disabled while there is active data
activity, the data activity overlay will not be removed and will
be stuck there. This patch fixes that.

Change-Id: I4cc1a14bb2e2d85687752657608e5989adfe9af1

packages/SystemUI/src/com/android/systemui/statusbar/policy/NetworkController.java

@@ -968,6 +968,8 @@ public class NetworkController extends BroadcastReceiver {
                 combinedActivityIconId = mMobileActivityIconId;
                 combinedSignalIconId = mDataSignalIconId; // set by updateDataIcon()
                 mContentDescriptionCombinedSignal = mContentDescriptionDataType;
+            } else {
+                mMobileActivityIconId = 0;
             }
         }