fix NPE in race condition.

import com.android.bandwidthtest.NetworkState.StateTransitionDirection;

import com.android.internal.util.AsyncChannel;

import junit.framework.Assert;

import java.io.IOException;

import java.net.UnknownHostException;

import java.util.List;

                } catch (InterruptedException e) {

                    e.printStackTrace();

                }

                if (mNetworkInfo == null) {

                    Log.v(LOG_TAG, "Do not have networkInfo! Force fetch of network info.");

                    mNetworkInfo = mCM.getActiveNetworkInfo();

                    Assert.assertNotNull(mNetworkInfo);

                }

                if ((mNetworkInfo.getType() != networkType) ||

                        (mNetworkInfo.getState() != expectedState)) {

                    Log.v(LOG_TAG, "network state for " + mNetworkInfo.getType() +