#354

backend/app/controllers/post_versions_controller.rb

@@ -49,10 +49,10 @@ class PostVersionsController < ApplicationController
 
     rows.map do |row|
       cur_tags =
-          Array(normalise_json(row.tags_json))
+          normalise_json(row.tags_json)
           .map { Post.tag_snapshot_literal(_1) }
       prev_tags =
-          Array(normalise_json(row.attributes['prev_tags_json']))
+          (normalise_json(row.attributes['prev_tags_json']) || [])
           .map { Post.tag_snapshot_literal(_1) }
 
       { post_id: row.post_id,