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/app/controllers/posts_controller.rb

@@ -88,7 +88,7 @@ class PostsController < ApplicationController
     original_created_from = params[:original_created_from]
     original_created_before = params[:original_created_before]
 
-    post = Post.new(title:, url:, thumbnail_base: '', uploaded_user: current_user,
+    post = Post.new(title:, url:, thumbnail_base: nil, uploaded_user: current_user,
                     original_created_from:, original_created_before:)
     post.thumbnail.attach(thumbnail)
     if post.save