From d42cb7b7908a4787e40811a7f343b8e74a8a21f8 Mon Sep 17 00:00:00 2001
From: Quincy Morgan <quincy.morgan@icloud.com>
Date: Thu, 6 Jun 2019 09:20:57 -0400
Subject: [PATCH] Fix issue where iD could crash upon save if user had edits
 stored before iD 2.15 (close #6496)

---
 modules/core/history.js | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/modules/core/history.js b/modules/core/history.js
index 518cba0a6..acb0d97d5 100644
--- a/modules/core/history.js
+++ b/modules/core/history.js
@@ -323,9 +323,11 @@ export function coreHistory(context) {
             } else {
                 var s = new Set();
                 _stack.slice(1, _index + 1).forEach(function(state) {
-                    state.photoOverlaysUsed.forEach(function(photoOverlay) {
-                        s.add(photoOverlay);
-                    });
+                    if (state.photoOverlaysUsed && Array.isArray(state.photoOverlaysUsed)) {
+                        state.photoOverlaysUsed.forEach(function(photoOverlay) {
+                            s.add(photoOverlay);
+                        });
+                    }
                 });
                 return Array.from(s);
             }