Index: wp-includes/js/customize-loader.dev.js
===================================================================
--- wp-includes/js/customize-loader.dev.js	(revision 20376)
+++ wp-includes/js/customize-loader.dev.js	(working copy)
@@ -21,6 +21,14 @@
 		open: function( params ) {
 			params.customize = 'on';
 
+			window.location.hash = '#customize';
+
+			var hash = window.location.hash;
+			setInterval( function() {
+				if ( window.location.hash != hash )
+					Loader.close();
+			}, 100);
+
 			this.iframe = $( '<iframe />', {
 				src: this.base + '?' + jQuery.param( params )
 			}).appendTo( this.element );
@@ -31,7 +39,8 @@
 		},
 		close: function() {
 			this.element.fadeOut( 200, function() {
-				Loader.iframe.remove();
+				if ( Loader.iframe )
+					Loader.iframe.remove();
 				Loader.iframe = null;
 				Loader.body.removeClass( 'customize-active full-overlay-active' );
 			});