Fix possible NPE

import android.preference.Preference.OnPreferenceClickListener;

import android.preference.PreferenceGroup;

import android.preference.PreferenceScreen;

import android.util.Log;

import android.view.inputmethod.InputMethodSubtype;

import java.util.TreeSet;

public final class SettingsFragment extends InputMethodSettingsFragment

        implements SharedPreferences.OnSharedPreferenceChangeListener {

    private static final String TAG = SettingsFragment.class.getSimpleName();

    private static final boolean DBG_USE_INTERNAL_USER_DICTIONARY_SETTINGS = false;

    private ListPreference mVoicePreference;

    @Override

    public void onSharedPreferenceChanged(final SharedPreferences prefs, final String key) {

        (new BackupManager(getActivity())).dataChanged();

        final Activity activity = getActivity();

        if (activity == null) {

            // TODO: Introduce a static function to register this class and ensure that

            // onCreate must be called before "onSharedPreferenceChanged" is called.

            Log.w(TAG, "onSharedPreferenceChanged called before activity starts.");

            return;

        }

        (new BackupManager(activity)).dataChanged();

        final Resources res = getResources();

        if (key.equals(Settings.PREF_POPUP_ON)) {

            setPreferenceEnabled(Settings.PREF_KEY_PREVIEW_POPUP_DISMISS_DELAY,