Fix Hotspot & tethering settings crash

- Cannot omit addPreferencesFromResource even if UI is restricted

Bug: 287172382
Test: manual test
atest -c WifiTetherSettingsTest

Change-Id: I1f5c0215a635fddefe7eaa20c1d765634b505121

src/com/android/settings/network/tether/TetherSettings.java

@@ -148,12 +148,13 @@ public class TetherSettings extends RestrictedSettingsFragment
     @Override
     public void onCreate(Bundle icicle) {
         super.onCreate(icicle);
+        // Even when the UI is restricted, addPreferencesFromResource cannot be omitted.
+        addPreferencesFromResource(R.xml.tether_prefs);
         setIfOnlyAvailableForAdmins(true);
         if (isUiRestricted()) {
             return;
         }
 
-        addPreferencesFromResource(R.xml.tether_prefs);
         mContext = getContext();
         mDataSaverBackend = new DataSaverBackend(mContext);
         mDataSaverEnabled = mDataSaverBackend.isDataSaverEnabled();

tests/robotests/src/com/android/settings/network/tether/TetherSettingsTest.java

@@ -131,10 +131,12 @@ public class TetherSettingsTest {
     @Test
     @Config(shadows = ShadowRestrictedSettingsFragment.class)
     public void onCreate_isUiRestricted_doNotSetupViewModel() {
+        doNothing().when(mTetherSettings).addPreferencesFromResource(anyInt());
         when(mTetherSettings.isUiRestricted()).thenReturn(true);
 
         mTetherSettings.onCreate(null);
 
+        verify(mTetherSettings).addPreferencesFromResource(anyInt());
         verify(mTetherSettings, never()).setupViewModel();
     }