From 16cd879e083cd81d5b39a4917b308675e2e099b7 Mon Sep 17 00:00:00 2001
From: r888888888 <r888888888@gmail.com>
Date: Mon, 27 Feb 2017 15:22:15 -0800
Subject: [PATCH] potential fix for #2900: Post Versions JSON API failure -
 undefined method join

---
 app/models/post_archive.rb | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/app/models/post_archive.rb b/app/models/post_archive.rb
index fa4e044c2..8b92f1560 100644
--- a/app/models/post_archive.rb
+++ b/app/models/post_archive.rb
@@ -221,6 +221,8 @@ class PostArchive < ActiveRecord::Base
 
     if previous
       delta[:unchanged_tags] = tag_array & previous.tag_array
+    else
+      delta[:unchanged_tags] = []
     end
 
     delta