when adding new save, eg a video, will not save

[xconan1]

不具合に関するissueの場合は下記テンプレートの利用をお願いします/When you report an issue, please use the following template.

• 発生した問題の詳細/Trouble details
  when trying to save a new video, it will state "This picture was already saved. Do you re-save this picture?"
• 発生したURL/URL
  pixiv.net
• 再現手順/Steps to reproduce
  open up pixiv.net

1. save a video by clicking on ankpixiv icon in toolbar
2. see another video wanting to save by the same author maybe also posted on same date,
   reclick on ankpixiv icon
3. should see "This picture was already saved. Do you re-save this picture?" pop up

• Ank Pixiv Toolのバージョン/Ank Pixiv Tool Version 3.0.12
• ブラウザのバージョン/Browser Version
  comodo icedragon 61.0.0.20 based on mozilla firefox 61
• 特記事項(設定や使用中のアドオンなど)/Special notes(configurations, add-on list, etc.)
• ログ(content側, DEBUGレベル以上)/Log(content script, >=DEBUG level)
• ログ(background側, DEBUGレベル以上)/Log(background script, >=DEBUG level)