DefaultHttpClient 在oppo A57手机上网络请求报错
使用的库是xutils2.6.14，oppo A57 上调试的时候，请求接口时报错，但是其他手机都正常；
com.lidroid.xutils.exception.HttpException:
java.io.IOException: Attempt to invoke virtual method 'boolean java.lang.String.contains(java.lang.CharSequence)' on a null object reference
接入xutils2.6.14源码库查看报错是：
06-11 11:37:20.792 W/System.err: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.contains(java.lang.CharSequence)' on a null object reference
06-11 11:37:20.794 W/System.err: at org.apache.http.protocol.RequestUserAgent.process(RequestUserAgent.java:83)
06-11 11:37:20.794 W/System.err: at org.apache.http.protocol.BasicHttpProcessor.process(BasicHttpProcessor.java:295)
06-11 11:37:20.794 W/System.err: at org.apache.http.protocol.HttpRequestExecutor.preProcess(HttpRequestExecutor.java:165)
06-11 11:37:20.794 W/System.err: at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:418)
06-11 11:37:20.794 W/System.err: at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:560)
06-11 11:37:20.795 W/System.err: at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:492)
06-11 11:37:20.795 W/System.err: at com.lidroid.xutils.http.HttpHandler.sendRequest(HttpHandler.java:125)
06-11 11:37:20.795 W/System.err: at com.lidroid.xutils.http.HttpHandler.doInBackground(HttpHandler.java:181)
06-11 11:37:20.795 W/System.err: at com.lidroid.xutils.http.HttpHandler.doInBackground(HttpHandler.java:40)
06-11 11:37:20.795 W/System.err: at com.lidroid.xutils.task.PriorityAsyncTask$1.call(PriorityAsyncTask.java:67)
06-11 11:37:20.795 W/System.err: at java.util.concurrent.FutureTask.run(FutureTask.java:237)
06-11 11:37:20.795 W/System.err: at com.lidroid.xutils.task.PriorityRunnable.run(PriorityRunnable.java:16)
06-11 11:37:20.795 W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
06-11 11:37:20.795 W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
06-11 11:37:20.795 W/System.err: at java.lang.Thread.run(Thread.java:818)
