Fix tethering summary when airplane mode is off

When airplane mode is off, fall back to default summary
(tether off summary). It should be fine because once tether
state get updated again, it will go through original listener
to update the summary.

Change-Id: Iba9b56f452e72365ea964d841ee156a2625c0ae1
Fixes: 79721162
Test: RunSettingsRoboTests

src/com/android/settings/wifi/tether/WifiTetherPreferenceController.java

@@ -44,6 +44,7 @@ public class WifiTetherPreferenceController extends AbstractPreferenceController
     private static final String WIFI_TETHER_SETTINGS = "wifi_tether";
     private static final IntentFilter AIRPLANE_INTENT_FILTER = new IntentFilter(
             Intent.ACTION_AIRPLANE_MODE_CHANGED);
+    private static final int ID_NULL = -1;
 
     private final ConnectivityManager mConnectivityManager;
     private final String[] mWifiRegexs;
@@ -152,7 +153,7 @@ public class WifiTetherPreferenceController extends AbstractPreferenceController
         public void onReceive(Context context, Intent intent) {
             String action = intent.getAction();
             if (Intent.ACTION_AIRPLANE_MODE_CHANGED.equals(action)) {
-                clearSummaryForAirplaneMode();
+                clearSummaryForAirplaneMode(R.string.wifi_hotspot_off_subtext);
             }
         }
     };
@@ -194,10 +195,16 @@ public class WifiTetherPreferenceController extends AbstractPreferenceController
     }
 
     private void clearSummaryForAirplaneMode() {
+        clearSummaryForAirplaneMode(ID_NULL);
+    }
+
+    private void clearSummaryForAirplaneMode(int defaultId) {
         boolean isAirplaneMode = Settings.Global.getInt(mContext.getContentResolver(),
                 Settings.Global.AIRPLANE_MODE_ON, 0) != 0;
         if (isAirplaneMode) {
             mPreference.setSummary(R.string.wifi_tether_disabled_by_airplane);
+        } else if (defaultId != ID_NULL){
+            mPreference.setSummary(defaultId);
         }
     }
     //