From 6e38c368042843a2b6527019b794fedb8590bec2 Mon Sep 17 00:00:00 2001
From: Dan Stillman <dstillman@zotero.org>
Date: Sat, 7 Mar 2020 03:38:10 -0500
Subject: [PATCH] Don't update Extra field if missing in fromJSON()

Harmless regression from recent changes
---
 chrome/content/zotero/xpcom/data/item.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/chrome/content/zotero/xpcom/data/item.js b/chrome/content/zotero/xpcom/data/item.js
index b303a2507c..f5a1fed28c 100644
--- a/chrome/content/zotero/xpcom/data/item.js
+++ b/chrome/content/zotero/xpcom/data/item.js
@@ -4423,7 +4423,9 @@ Zotero.Item.prototype.fromJSON = function (json, options = {}) {
 		}
 	}
 	
-	this.setField('extra', Zotero.Utilities.Internal.combineExtraFields(extra, extraFields));
+	if (extra || extraFields.size || this.getField('extra')) {
+		this.setField('extra', Zotero.Utilities.Internal.combineExtraFields(extra, extraFields));
+	}
 	
 	if (json.collections || this._collections.length) {
 		this.setCollections(json.collections);