Preview of dataset fails if the 1st column is empty

[ecoloy]

Describe the bug
Preview of dataset fails when uploading an Excel file with the first blank column

To Reproduce
Steps to reproduce the behavior:

1. Go to Management > Data Preparation > Dataset
2. Click on 'Generate new dataset'
3. Select 'File' type
4. Upload this file test-without 1 col.xlsx
5. See preview

Expected behavior
Previews should work normally, such as uploading the same files to the datasource.

Screenshots
Datasource preview

Dataset preview

Desktop (please complete the following information):

• OS: Mac OS X
• Browser: Chrome
• Version: 71.0

Additional context
Add any other context about the problem here.

[joohokim1]

@ecoloy
I'll see first, then ask @sang-hee-lee for help if needed.

[joohokim1]

@ecoloy @sang-hee-lee

On PrepDatasetFileService.java:553, it's trying to add an element to an empty list by index.
@ksparknot will take this issue.

PrepDatasetFileService.java:553에서 빈 목록에 대해 인덱스를 갖고 element를 추가하려고 합니다.
@ksparknot 님께서 이후 진행하실 예정입니다.

[joohokim1]

It looks like working by now on master.
Although it's a bit different from datasource's, I think showing the columns with empty values would be better in data preparation.

지금 master에서 잘 동작하는 것 같습니다.
데이터 소스와는 조금 다르지만, data preparation에서는 지금처럼 공백 컬럼이 나오는 것이 더 좋을 듯 보입니다.

[joohokim1]

Closing with no PR.