Check for data usage cycle before using it.

import android.telephony.TelephonyManager;

import android.text.format.DateUtils;

import android.util.Log;

import android.util.Pair;

import android.util.Range;

import com.android.internal.R;

import com.android.internal.annotations.VisibleForTesting;

import java.time.ZonedDateTime;

import java.util.Date;

import java.util.Iterator;

import java.util.Locale;

public class DataUsageController {

            final NetworkStatsHistory history = session.getHistoryForNetwork(template, FIELDS);

            final long now = System.currentTimeMillis();

            final long start, end;

            if (policy != null) {

                final Pair<ZonedDateTime, ZonedDateTime> cycle = NetworkPolicyManager

                        .cycleIterator(policy).next();

                start = cycle.first.toInstant().toEpochMilli();

                end = cycle.second.toInstant().toEpochMilli();

            final Iterator<Range<ZonedDateTime>> it =

                    (policy != null) ? policy.cycleIterator() : null;

            if (it != null && it.hasNext()) {

                final Range<ZonedDateTime> cycle = it.next();

                start = cycle.getLower().toInstant().toEpochMilli();

                end = cycle.getUpper().toInstant().toEpochMilli();

            } else {

                // period = last 4 wks

                end = now;