From 10e93c557bb4e5d16b325aa4bea68bb990c66982 Mon Sep 17 00:00:00 2001
From: Andrew Ozz <azaozz@git.wordpress.org>
Date: Tue, 26 Jul 2016 22:05:39 +0000
Subject: [PATCH] TinyMCE, wpView: bail early when the iframe node is not
 attached to the DOM. We can't load any HTML in it as here is no
 `iframe.contentWindow` in these cases.

See #36434.

git-svn-id: https://develop.svn.wordpress.org/trunk@38157 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/js/mce-view.js | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/wp-includes/js/mce-view.js b/src/wp-includes/js/mce-view.js
index d2c29f7e88..10e33cc3b0 100644
--- a/src/wp-includes/js/mce-view.js
+++ b/src/wp-includes/js/mce-view.js
@@ -539,6 +539,14 @@
 						dom.add( node, 'span', { 'class': 'wpview-end' } );
 					} );
 
+					// Bail if the iframe node is not attached to the DOM.
+					// Happens when the view is dragged in the editor.
+					// There is a browser restriction when iframes are moved in the DOM. They get emptied.
+					// The iframe will be rerendered after dropping the view node at the new location.
+					if ( ! iframe.contentWindow ) {
+						return;
+					}
+
 					iframeDoc = iframe.contentWindow.document;
 
 					iframeDoc.open();