Fix NullPointerException of DataUsageList

Fix: 296357959
Test: manual - on DataUsageList page
Change-Id: I303aa8ae1ba5db8f23dbc3b68b9ff4e05a0936a0

src/com/android/settings/datausage/DataUsageList.java

@@ -538,6 +538,9 @@ public class DataUsageList extends DataUsageBaseFragment
 
     @VisibleForTesting
     void startAppDataUsage(AppItem item) {
+        if (mCycleData == null) {
+            return;
+        }
         final Bundle args = new Bundle();
         args.putParcelable(AppDataUsage.ARG_APP_ITEM, item);
         args.putParcelable(AppDataUsage.ARG_NETWORK_TEMPLATE, mTemplate);