fix get data empty and then exception

Author: yangsen

library/src/main/java/com/qiniu/android/storage/UploadData.java

@@ -89,7 +89,7 @@ long uploadSize() {
     void clearUploadState() {
         etag = null;
         md5 = null;
-        state = State.WaitToUpload;
+        state = State.NeedToCheck;
     }
 
     void checkStateAndUpdate() {

library/src/main/java/com/qiniu/android/storage/UploadInfoV1.java

@@ -305,7 +305,7 @@ private UploadBlock loadBlockData(UploadBlock block) throws IOException {
         // 已经加载过 block 数据
         // 没有需要上传的片 或者 有需要上传片但是已加载过片数据
         UploadData nextUploadData = block.nextUploadDataWithoutCheckData();
-        if (nextUploadData.getState() == UploadData.State.WaitToUpload) {
+        if (nextUploadData.getState() == UploadData.State.WaitToUpload && nextUploadData.data != null) {
             return block;
         }