Fix NPE in advanced settings

Bug: 5723974
Change-Id: I9904b6adb2b51f1511f932ef7cba8f6558417061

src/com/android/settings/wifi/AdvancedWifiSettings.java

@@ -75,11 +75,13 @@ public class AdvancedWifiSettings extends SettingsPreferenceFragment
 
         CheckBoxPreference watchdogEnabled =
             (CheckBoxPreference) findPreference(KEY_ENABLE_WIFI_WATCHDOG);
+        if (watchdogEnabled != null) {
             watchdogEnabled.setChecked(Secure.getInt(getContentResolver(),
                         Secure.WIFI_WATCHDOG_ON, 1) == 1);
 
             //TODO: Bring this back after changing watchdog behavior
             getPreferenceScreen().removePreference(watchdogEnabled);
+        }
 
         ListPreference frequencyPref = (ListPreference) findPreference(KEY_FREQUENCY_BAND);