From d415d4cf11dc8f55adfe5dc51cca2c535f52e859 Mon Sep 17 00:00:00 2001
From: Steve Howell <showell30@yahoo.com>
Date: Thu, 11 May 2017 09:28:33 -0700
Subject: [PATCH] Add error handling in watch_manual_resize().

We now explicitly complain if a caller passes in a bad
selector to this function and return undefined.
---
 static/js/message_edit.js | 4 +++-
 static/js/resize.js       | 9 ++++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/static/js/message_edit.js b/static/js/message_edit.js
index b7ef6237eb..107bbf7855 100644
--- a/static/js/message_edit.js
+++ b/static/js/message_edit.js
@@ -223,7 +223,9 @@ function edit_message(row, raw_content) {
         copy_message.remove();
         var edit_id = "#message_edit_content_" + rows.id(row);
         var listeners = resize.watch_manual_resize(edit_id);
-        currently_editing_messages[rows.id(row)].listeners = listeners;
+        if (listeners) {
+            currently_editing_messages[rows.id(row)].listeners = listeners;
+        }
         composebox_typeahead.initialize_compose_typeahead(edit_id, {emoji: true, stream: true});
     }
 
diff --git a/static/js/resize.js b/static/js/resize.js
index 965cd33612..4ce7bb11af 100644
--- a/static/js/resize.js
+++ b/static/js/resize.js
@@ -167,8 +167,15 @@ function left_userlist_get_new_heights() {
 
 exports.watch_manual_resize = function (element) {
     return (function on_box_resize(cb) {
+        var box = document.querySelector(element);
+
+        if (!box) {
+            blueslip.error('Bad selector in watch_manual_resize: ' + element);
+            return;
+        }
+
         var meta = {
-            box: document.querySelector(element),
+            box: box,
             height: null,
             mousedown: false,
         };