修正了String类型的为null的时候对外的数据统一返回""字符串

foudations/mogo-connection/src/main/java/com/mogo/connection/socket/SocketManager.java

@@ -93,6 +93,7 @@ public class SocketManager implements IMogoSocketManager, OnSocketReceiveCallbac
                 while ( iterator.hasNext() ) {
                     IMogoOnMessageListener listener = iterator.next();
                     if ( listener != null ) {
+                        Logger.d(TAG, "received msg ==" + payload.getPayload().toStringUtf8());
                         listener.onMsgReceived( GsonUtil.objectFromJson( payload.getPayload().toStringUtf8(), listener.target() ) );
                     }
                 }