feat: posts.thumbnail_base を Nullable に（#75） (#198)

Merge remote-tracking branch 'origin/main' into feature/075

#75

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #198

backend/lib/tasks/sync_nico.rake

@@ -49,7 +49,7 @@ namespace :nico do
       unless post
         title = datum['title']
         url = "https://www.nicovideo.jp/watch/#{ datum['code'] }"
-        thumbnail_base = fetch_thumbnail.(url) || '' rescue ''
+        thumbnail_base = fetch_thumbnail.(url) rescue nil
         post = Post.new(title:, url:, thumbnail_base:, uploaded_user: nil)
         if thumbnail_base.present?
           post.thumbnail.attach(